U.S. patent number 7,029,820 [Application Number 10/265,323] was granted by the patent office on 2006-04-18 for support for lithographic printing plate and presensitized plate and method of producing lithographic printing plate.
This patent grant is currently assigned to Fuji Photo Film Co., Ltd.. Invention is credited to Tadashi Endo, Hisashi Hotta, Yoshinori Hotta.
United States Patent |
7,029,820 |
Hotta , et al. |
April 18, 2006 |
Support for lithographic printing plate and presensitized plate and
method of producing lithographic printing plate
Abstract
Disclosed is a support for a lithographic printing plate
obtainable by performing at least graining treatment on an aluminum
plate, having on its surface thereof, a grain shape with a
structure in which a grained structure with medium undulation of
0.5 to 5 .mu.m average aperture diameter and a grained structure
with small undulation of 0.01 to 0.2 .mu.m average aperture
diameter are superimposed, and a presensitized plate provided with
an image recording layer on the support for a lithographic printing
plate. By using this presensitized plate, a balance between scum
resistance and press life when a lithographic printing plate is
produced therefrom, which has been in a trade-off relation in the
past, can be maintained at a high level.
Inventors: |
Hotta; Yoshinori (Shizuoka,
JP), Hotta; Hisashi (Shizuoka, JP), Endo;
Tadashi (Shizuoka, JP) |
Assignee: |
Fuji Photo Film Co., Ltd.
(Kanagawa, JP)
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Family
ID: |
27347660 |
Appl.
No.: |
10/265,323 |
Filed: |
October 7, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20030165768 A1 |
Sep 4, 2003 |
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Foreign Application Priority Data
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Oct 5, 2001 [JP] |
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2001-309304 |
Nov 15, 2001 [JP] |
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2001-349926 |
Dec 3, 2001 [JP] |
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2001-368258 |
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Current U.S.
Class: |
430/165; 205/213;
205/214; 430/278.1; 430/281.1; 430/302 |
Current CPC
Class: |
B41N
3/03 (20130101); B41N 3/04 (20130101); B41N
3/034 (20130101) |
Current International
Class: |
G03F
7/023 (20060101); G03C 1/77 (20060101); G03F
7/09 (20060101) |
Field of
Search: |
;430/270.1,278.1,302,165,281.1 ;205/213,214 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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7-61161 |
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Mar 1995 |
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JP |
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07-271039 |
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Oct 1995 |
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JP |
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08-258440 |
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Oct 1996 |
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JP |
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08-300843 |
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Nov 1996 |
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JP |
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8-300844 |
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Nov 1996 |
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JP |
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9-234971 |
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Sep 1997 |
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JP |
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10-16419 |
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Jan 1998 |
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JP |
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10-35133 |
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Feb 1998 |
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JP |
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11-99758 |
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Apr 1999 |
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JP |
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11-115340 |
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Apr 1999 |
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JP |
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11-167204 |
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Jun 1999 |
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JP |
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11-167207 |
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Jun 1999 |
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JP |
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11-174689 |
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Jul 1999 |
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JP |
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11-208138 |
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Aug 1999 |
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JP |
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2001-166462 |
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Jun 2001 |
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JP |
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2001-213066 |
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Aug 2001 |
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JP |
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2001-232965 |
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Aug 2001 |
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JP |
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WO-200234544 |
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May 2002 |
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WO |
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Primary Examiner: Chu; John S.
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A support for a lithographic printing plate obtainable by
performing at least electrochemical graining treatment by an
electrolyte containing a hydrochloric acid and subsequent alkali
etching treatment in which an amount of etching is 0.5 g/m.sup.2 or
less on an aluminum plate, having on its surface thereof, a grain
shape with a structure in which a grained structure with medium
undulation of 0.5 to 5 .mu.m average aperture diameter and a
grained structure with small undulation of 0.01 to 0.18 .mu.m
average aperture diameter are superimposed.
2. A support for a lithographic printing plate obtainable by
performing at least electrochemical graining treatment by an
electrolyte containing a hydrochloric acid and subsequent alkali
etching treatment in which an amount of etching is 0.5 g/m.sup.2 or
less on an aluminum plate, having on its surface thereof, a grain
shape with a structure in which a grained structure with large
undulation of 5 to 100 .mu.m average wavelength, a grained
structure with medium undulation of 0.5 to 5 .mu.m average aperture
diameter, and a grained structure with small undulation of 0.01 to
0.18 .mu.m average aperture diameter are superimposed.
3. The support for a lithographic printing plate according to claim
1, in which an average of ratios of depths to the aperture
diameters of the aforementioned grained structure with small
undulation is 0.2 or more.
4. The support for a lithographic printing plate according to claim
1, including a water receptive layer with thermal conductivity of
0.05 to 0.5W/(mK) on the surface.
5. A method of producing a lithographic printing plate by exposing
a presensitized plate provided with an image recording layer on the
support for a lithographic printing plate according to claim 1 and
subsequently developing with a developer containing substantially
no alkali metal silicate.
6. A method of producing a lithographic printing plate by exposing
a presensitized plate provided with an image recording layer on the
support for a lithographic printing plate according to claim 2 and
subsequently developing with a developer containing substantially
no alkali metal silicate.
7. The support for a lithographic printing plate according to claim
1, in which the grained structure with the medium undulation is
formed by electrochemical graining treatment by an electrolyte
containing a nitric acid and the grained structure with small
undulation is formed by the electrochemical graining treatment by
an electrolyte containing a hydrochloric acid.
8. The support for a lithographic printing plate according to claim
4, in which the water receptive layer is obtainable by performing
anodizing treatment on the aluminum plate to make an anodized layer
and pore widening treatment to the anodized layer.
9. The support for a lithographic printing plate according to claim
4, in which the water receptive layer is a SiO.sub.2 layer.
10. The support for a lithographic printing plate according to
claim 4, in which the water receptive layer is obtainable by
sputtering process.
11. The support for a lithographic printing plate according to
claim 10, in which the water receptive layer is an Al.sub.2O.sub.3
layer.
12. A presensitized plate provided with an image recording layer on
the support for a lithographic printing plate according to claim 1,
in which the image recording layer is a thermosensitive layer of
the thermal positive type containing an alkali-soluble
high-molecular compound and a photothermal conversion agent.
13. A presensitized plate provided with an image recording layer on
the support for a lithographic printing plate according to claim 1,
in which the image recording layer is a photosensitive layer of the
photopolymer type containing a compound containing ethylenic
unsaturated bonding capable of addition polymerization, a
photopolymerization initiator and a high-molecular binding
agent.
14. A presensitized plate provided with an image recording layer on
the support for a lithographic printing plate according to claim 1,
in which the image recording layer is a photosensitive layer of the
conventional positive type containing an o-quinonediazide compound
and a high-molecular compound that is water-insoluble and
alkali-soluble.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a support for a lithographic
printing plate, a presensitized plate, and a method of producing a
lithographic printing plate. More particularly, the present
invention relates to a support for a lithographic printing plate
having an optimum surface shape achieving both high scum resistance
and long press life when a lithographic printing plate is produced,
a presensitized plate using the support for a lithographic printing
plate, and a method of producing a lithographic printing plate
excellent in scum resistance and press life.
2. Description of the Related Art
Lithography is a printing process which makes use of a nature that
water and oil are essentially unmixable with each other. On the
printing plate surface of a lithographic printing plate used in
this process, areas that receive water and repel an oil-based ink
(hereinafter referred to as "non-image areas") and the other areas
that repel water and receive an oil-based ink (hereinafter referred
to as "image areas") are formed.
Since an aluminum support for a lithographic printing plate used
for a lithographic printing plate (hereinafter referred to simply
as "a support for a lithographic printing plate") is used as such
that the surface thereof plays a role of non-image areas, various
conflicting performances are required, such as excellency in water
wettability and water receptivity as well as excellency in contact
characteristics with an image recording layer provided on the
support.
If the water wettability of a support is too low, an ink is
attached to non-image areas at the time of printing, thereby
causing a dirt on a blanket cylinder and further a so-called scum.
In addition, if the water receptivity is too low, a shadow portion
may be plugged unless much fountain solution is applied at the time
of printing. Therefore, a so-called water range is narrowed.
In order to obtain a support for a lithographic printing plate
excellent in these performances, generally asperities are provided
for the surface of an aluminum plate by performing graining
(graining treatment) thereon. As shown below, various shapes of the
asperities are proposed. JP 8-300844 A (the term "JP XX-XXXXXX A"
as used herein means an "unexamined published Japanese patent
application"), describes a triple grained structure having a
grained structure of large undulation, a grained structure of
medium undulation, and a grained structure of small undulation,
with aperture diameters of the grained structures of medium and
small undulations specified. JP 11-99758 A and JP 11-208138 A
describe specifying the diameter of a grained structure with small
undulation in the double structure with a grained structure of
large and small undulations. JP 11-167207 A describes an art
providing large and small double concave portions (pits) and
further fine protrusions JP 2023476 B (the term "JP XX-XXXXXX B" as
used herein means an "examined Japanese patent publication")
describes a double structure with the aperture diameters specified.
JP 8-300843 A describes a double structure with a factor a30
indicating smoothness of a surface specified. JP 10-35133 A
describes a structure with the ratio of diameters of pits
superimposed at a time of a plurality of electrochemical graining
treatments (hereinafter referred also to as an "electrolytic
graining treatment").
Methods to be used for this graining include a mechanical graining
treatments such as ball graining, brush graining, wire graining and
blast graining, an electrolytic graining treatment performing
electrolytic etching on an aluminum plate in an electrolyte
containing hydrochloric aid and/or nitric acid, and a composite
graining treatment combining a mechanical graining treatment and an
electrolytic graining treatment as described in U.S. Pat. No.
4,476,006 and the like.
SUMMARY OF THE INVENTION
However, in the aforementioned related arts, since scum resistance
and press life are traded off, both cannot be achieved at the same
time.
Therefore, it is the first object of the present invention to solve
this problem and provide a presensitized plate which is excellent
in both scum resistance and high press life can be achieved, and a
support for a lithographic printing plate used for the
presensitized plate. In addition, it is the second object of the
present invention to provide a method of producing a lithographic
printing plate excellent in scum resistance and press life.
In the meantime, with the development of an image formation
technology, a direct plate making is becoming possible by scanning
a laser beam with a narrowed-down beam on the surface of the
presensitized plate to directly form a lettered original, an image
original or the like on the presensitized plate, dispensing with a
film original.
Particularly, a presensitized plate called a thermal type or a heat
mode type where an image is formed with heat obtained by generating
photothermal conversion in an image recording layer with
irradiation of an infrared-ray laser beam is proposed in a variety
of forms since it has a merit that the plate can be used in a
bright room. Among these presensitized plates, a so-called thermal
positive type presensitized plate which forms a positive image
allowing an image recording layer to be alkali-soluble by heat uses
a subtle change in the intermolecular interaction of a binder in
the image recording layer by a laser exposure as an image formation
principle. Therefore, a difference between the alkali-soluble state
in the exposed area and the non-alkali-soluble state in the
unexposed area is small. For that reason, in order to obtain a
practicable clear discrimination, used are means for forming an
image recording layer structure with suppressed development
solubility of the unexposed area by providing a surface slightly
soluble layer in a developer as the top layer of the image
recording layer, means for suppressing the development solubility
of the unexposed area by adding to the developer a low absorbable
development inhibitor component to the unexposed area on the
surface of the image recording layer, and the like.
If the surface slightly soluble layer is, however, damaged due to
some cause, even an area which is supposed to be an image area
becomes soluble in the developer. That is, practically, a printing
plate is too easily damaged. For that reason, it is the status quo
that handling of the presensitized plate at the time of working is
difficult, since scratch-like non-image portions are generated even
by a subtle touching such as hitting of the plates when handling
the presensitized plate, a subtle rubbing with interleaving sheets,
or a contact of fingers with plate surface. Although
countermeasures are taken to lower coefficient of friction by
providing a layer having a fluorine-containing surfactant or a wax
on the surface of the image recording layer in order to improve
damage resistance, they are not sufficient.
In the meantime, in order to increase discrimination, efficiency of
development is also studied, an attempt is made to provide a water
receptive layer by silicate treatment or an alkali-soluble
undercoat layer (alkali-soluble layer) between the image recording
layer and the support. According to these methods, it is certainly
possible to ensure development capacity to some extent and obtain a
development latitude within a practical range. However, contact
characteristics between the image recording layer and the support
deteriorate. In addition, if the surface shape of the support is
smoothened to remove deep concave portions existent on the support
surface which cause residual layers in order to increase scum
resistance, press life largely deteriorates, thereby the
presensitized plate becoming impractical. For this reason, a
presensitized plate that is at a level that meets the requirements
of easy printing, that is excellent press life and high scum
resistance has not been materialized yet.
Such a presensitized plate of a type where an infrared absorbent
existent in the image recording layer develops a photothermal
conversion action thereof to generate a heat by exposure, and an
image is formed on the image recording layer by the generated heat
has also following problems.
That is, in a thermal type image formation like this, a heat is
generated by a photothermal conversion agent in a photosensitive
layer by a laser beam irradiation and triggers an image formation
reaction. However, since thermal conductivity of an aluminum
support subjected to graining treatment is much higher than that of
the image recording layer., a heat generated in the vicinity of an
interface between the image recording layer and the support
diffuses inside the support before it is sufficiently used for
image formation.
Consequently, in the case of the aforementioned thermal positive
type image recording layer, if a heat diffuses inside the support
and an alkali-soluble reaction is insufficient, a problem arises
that residual layers are produced in an area which is supposed to
be non-image areas, thus sensitivity becomes low, constituting an
essential problem with a thermal positive type image recording
layer. In addition, a thermal type presensitized plate like this
requires an infrared-ray absorbent having a photothermal converting
function. Since the molecular weights of these absorbents are
relatively large, their solubilities are low. In addition, these
absorbents are difficult to be removed since they are attached to
micro apertures (micropores) generated by anodizing treatment.
Therefore, a problem arises that residual layers are easily
produced in a development process with an alkali developer.
It is an object of a third aspect of the present invention to
provide a thermosensitive presensitized plate that overcomes the
defects of the aforementioned related arts. That is, the third
object is to provide a thermosensitive presensitized plate that is
capable of efficiently using heat for image formation, with high
sensitivity, long press life, and high scum resistance in non-image
areas, and a support for a lithographic printing plate used for the
presensitized plate.
In order to achieve the aforementioned first object, the inventors
have intensively studied the size of an asperity structure of the
surface of a support for a lithographic printing plate and their
combination to finally find out that a combination of asperities
with specified sizes can maintain a balance between scum resistance
and press life at a high level.
In order to achieve the aforementioned first object, the inventors
have also intensively studied the surface shape of a support for a
lithographic printing plate to finally find out that a specified
combination of surface roughness, surface area ratio and steepness
which are factors to indicate a surface shape obtained by using an
atomic force microscope can maintain a balance between scum
resistance and press life at a high level.
In addition, conventionally, in order to improve scum resistance
(resistance to dirtiness) of a lithographic printing plate, as a
general practice, a developer contains an alkali metal silicate
such that Si atoms are allowed to be attached to only non-image
areas obtained by removing an image recording layer, thus improving
water wettability of the non-image areas. If a developer containing
an alkali metal silicate is used for development, however, problems
occur such as that a solid substance attributable to SiO.sub.2
easily deposits, a gel attributable to SiO.sub.2 generates in a
neutralization treatment for treating the waste of the developer.
As a result, there are cases where non-image areas is whitened at
the time of development, or scum or sludge is generated at the time
of development.
In the meantime, when development is performed using a developer
containing substantially no alkali metal silicates, there is a
problem that, if the support for a lithographic printing plate is
not subjected to alkali metal silicate treatment, a phenomenon that
an ink is not easily removed when a printing machine stops and
printing is restarted after the lithographic printing plate is left
as it stands on the printing machine (deterioration in scum
resistance after being left) easily occurs.
The inventors have found out that, from a presensitized plate which
uses the aforementioned support for a lithographic printing plate,
a lithographic printing plate excellent in scum resistance after
being left can be obtained if development is performed with a
developer containing substantially no alkali metal silicates after
exposure even if the aforementioned support for a lithographic
printing plate is not subjected to the alkali metal silicate
treatment.
In addition, in order to achieve the aforementioned third object,
the inventors also have intensively studied a surface shape of the
support for a lithographic printing plate and a water receptive
layer provided thereon to finally find out that when surface
roughness, surface area ratio and steepness, as well as thermal
conductivity of the water receptive layer which are factors to
indicate a surface shape obtained by using an atomic force
microscope are used in a specific combination, high sensitivity and
long press life are exhibited, and scum is not easily generated in
non-image areas. That is, they have found that when a presensitized
plate with a specified surface shape (a grained structure with
medium undulation and a grained structure with small undulation)
and/or a specified surface shape physical properties (R.sub.a,
.DELTA.S, a30 and a60), provided with a water receptive layer
having thermal conductivity within a specified range thereon, and a
photothermal layer is further provided thereon is used, sensitivity
is high, and when a lithographic printing plate is produced, press
life is long and scum is not easily generated in the non-image
areas.
The inventors have completed the present invention based on these
findings.
That is, the present invention provides (1) to (7) to be described
below.
(1) A support for a lithographic printing plate obtainable by
performing at least graining treatment on an aluminum plate, having
on its surface thereof, a grain shape with a structure in which a
grained structure with medium undulation of 0.5 to 5 .mu.m average
aperture diameter and a grained structure with small undulation of
0.01 to 0.2 .mu.m average aperture diameter are superimposed (the
first aspect of the present invention).
(2) A support for a lithographic printing plate obtainable by
performing at least graining treatment on an aluminum plate, having
on its surface thereof, a grain shape with a structure in which a
grained structure with large undulation of 5 to 100 .mu.m average
wavelength, a grained structure with medium undulation of 0.5 to 5
.mu.m average aperture diameter, and a grained structure with small
undulation of 0.01 to 0.2 .mu.m average aperture diameter are
superimposed.
(3) The support for a lithographic printing plate according to (1)
or (2) mentioned above, in which an average of ratios of depths to
the aperture diameters of the aforementioned grained structure with
small undulation is 0.2 or more.
(4) A support for a lithographic printing plate, in which each of
R.sub.a, .DELTA.S, a30 and a60 obtained from the three-dimensional
data taken by measuring 50 .mu.m.quadrature. area on its surface at
512.times.512 points with an atomic force microscope satisfies the
following conditions as described in (i) to (iv) (the second aspect
of the present invention).
(i) R.sub.a: 0 45 .mu.m or more
(ii) .DELTA.S: 30% or more
(iii) a30: 55% or more
(iv) a60: 10% or less
In these conditions, R.sub.a indicates a surface roughness obtained
after removing components of wavelength 2 .mu.m or longer form the
aforementioned three-dimensional data.
.DELTA.S is obtained by the following equation from an actual area
S.sub.x calculated from the aforementioned three-dimensional data
with the approximation three-point method and a geometrically
measured area S.sub.0:
.DELTA.S=(S.sub.x-S.sub.0)/S.sub.0.times.100(%).
a30 and a60 indicate area ratio of an area of gradient 30.degree.
or more and an area of gradient 60.degree. or more, respectively,
obtained after removing components of wavelength 2 .mu.m or longer
from the aforementioned three-dimensional data.
A support for a lithographic printing plate that meets the
requirements of both first aspect and the second aspect of the
present invention is the particularly preferred form.
One of the preferable aspects is that a support for a lithographic
printing plate according to any one of the above (1) to (4) is
obtained by sequentially performing mechanical graining treatment,
alkali etching treatment, desmutting treatment with an acid, and
electrochemical graining treatment with an electrolyte containing
nitric acid electrochemical graining treatment with an electrolyte
containing hydrochloric acid, alkali etching treatment, and
desmutting treatment on an aluminum plate.
(5) The support for a lithographic printing plate according to any
one of (1) to (4) mentioned above, including a water receptive
layer with thermal conductivity of 0.05 to 0.5W/(mK) on the surface
(the third aspect of the present invention).
It is preferable when the aforementioned water receptive layer is
an anodized layer formed by performing anodizing treatment.
It is also preferable that density of the aforementioned water
receptive layer is 1,000 to 3,200 kg/m.sup.3 or porosity thereof is
20 to 70%.
It is more preferable that alkali metal silicate treatment is
performed on the aforementioned water receptive layer.
Further, it is more preferable that quantity of Si atom adsorbed by
this alkali metal silicate treatment is 1.0 to 15 mg/m.sup.2.
(6) A presensitized plate provided with an image recording layer on
the support for a lithographic printing plate according to any one
of (1) to (5) mentioned above.
When the support for a lithographic printing plate according to (5)
mentioned above is used, one of the preferable aspects is that the
aforementioned image recording layer is a thermosensitive layer
that contains a high-molecular compound insoluble in water and
soluble in an alkali and a photothermal conversion agent and of
which solubility to an alkali aqueous solution is changed by
heating.
In addition, when the support for a lithographic printing plate
according to (5) mentioned above is used, one of the preferable
aspects is that the aforementioned image recording layer includes a
lower layer provided on the hydrophilic support and its upper
thermosensitive layer, and the thermosensitive layer and/or the
lower layer contains a high-molecular material having acid
group.
(7) A method of producing a lithographic printing plate by exposing
the presensitized plate according to (6) mentioned above and
subsequently developing with a developer containing substantially
no alkali metal silicate.
As described below, if the support for a lithographic printing
plate of the first and second aspects according to the present
invention having an feature on its surface shape is used, a balance
between scum resistance and press life, which has been in a
trade-off relation in the past, can be maintained at a high
level.
Particularly, if a support for a lithographic printing plate of the
third aspect according to the present invention having a water
receptive layer of a specified thermal conductivity is used, a
thermosensitive presensitized plate where heat can be efficiently
utilized to form an image, the sensitivity is high, it exerts a
high press life and a dirt is hardly generated in non-image
areas.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view showing a concept of a brush graining process
used for mechanical graining treatment used in production of a
support for a lithographic printing plate according to the present
invention.
FIG. 2 is a graph showing an example of an trapezoidal current
waveform view used for electrochemical graining treatment used in
production of a support for a lithographic printing plate according
to the present invention.
FIG. 3 is a side view showing an example of a radial cell used for
electrochemical graining treatment using alternating current used
in production of a support for a lithographic printing plate
according to the present invention.
FIG. 4 is a schematic view of an anodizing device used for
anodizing treatment used in production of a support for a
lithographic printing plate according to the present invention.
FIG. 5 is a schematic view of a thermocomparator that can be used
to measure the thermal conductivity in a layer thickness direction
of the water receptive layer of a support for a lithographic
printing plate according to the present invention.
DETAILED DESCRIPTION
Hereafter, the present invention will be explained in detail.
[Support for Lithographic Printing Plate]
<Grain Shape on Surface>
A support for a lithographic printing plate according to the first
aspect of the present invention is characterized by having, on its
surface, a grain shape with a structure in which a grained
structure with medium undulation of 0.5 to 5 .mu.m average aperture
diameter and a grained structure with small undulation of 0.01 to
0.2 .mu.m average aperture diameter are superimposed.
According to the first aspect of the present invention, a grained
structure with medium undulation of 0.5 to 5 .mu.m average aperture
diameter has functions of retaining an image recording layer mainly
by anchoring effect so as to provide a long press life. If the
average aperture diameter of a pit of the grained structure with
medium undulation is less than 0.5 .mu.m, press life of the
lithographic printing plate may deteriorate due to decrease in
contact characteristics with the image recording layer provided as
an upper layer. On the other hand, if the average aperture diameter
of the pit of the grained structure with medium undulation exceeds
5 .mu.m, press life may deteriorate due to decrease in the number
of pit boundary areas playing a role of the anchor.
A grained structure with small undulation of 0.01 to 0.2 .mu.m
average aperture diameter superimposed on the aforementioned
grained structure with medium undulation mainly plays a role of
improving scum resistance. By combining the grained structure with
small undulation with the grained structure with medium undulation,
when fountain solution is supplied to the lithographic printing
plate at the time of printing, a water film is evenly formed on the
surface thereof, thereby generation of dirt in non-image areas
being suppressed. If the average aperture diameter of the pit of
the grained structure with small undulation is less than 0.01
.mu.m, a good effect of water film formation may not be obtained.
On the other hand, if the average aperture diameter of the pit of
the grained structure with small undulation exceeds 0.2 .mu.m, the
aforementioned effect of improving press life by the grained
structure with medium undulation may not be obtained since the
grained structure with medium undulation is broken.
With regard to the grained structure with small undulation, scum
resistance can be further improved by controlling not only the
aperture diameter but also a depth of the pit. That is, it is
preferable that the ratio of the depth with respect to the aperture
diameter of the grained structure with small undulation is 0.2 or
more. This reliably allows the evenly formed water film to be
retained on the surface and maintain scum resistance on the surface
of the non-image areas is maintained for a long period.
The aforementioned structure in which a grained structure with
medium undulation and a grained structure with small undulation are
superimposed may be a structure where further superimposed by a
grained structure with large undulation of 5 to 100 .mu.m average
wavelength.
The grained structure with large undulation has an effect of
increasing an amount of water retained in the surface of the
non-image areas of the lithographic printing plate. The more the
water retained is in the surface, the less affected the surface of
the non-image areas is by contamination in the atmosphere. This
allows obtaining non-image areas that is not easily get dirty even
though the printing plate is left as it stands during printing. In
addition, if the grained structure with large undulation is
superimposed, it is easier to visually inspect an amount of
fountain solution supplied to the surface of the printing plate at
the time of printing. Namely, inspectability of the lithographic
printing plate becomes excellent. If the average wavelength of the
grained structure with large undulation is less than 5 .mu.m, there
may be no difference from the grained structure with medium
undulation. If the average wavelength of the grained structure with
large undulation exceeds 100 .mu.m, inspectability of the printing
plate may be impaired since the exposed non-image areas appear
dazzling after exposure and development. It is preferable that the
average wavelength of the grained structure with large undulation
is 10 to 80 .mu.m.
In the support for a lithographic printing plate according to the
first aspect according to the present invention, following are
methods of measuring the average aperture diameter of the grained
structure with medium undulation on a surface, the average aperture
diameter and the average depths with respect thereto of the grained
structure with small undulation, and the average wavelength of the
grained structure with large undulation.
(1) Average Aperture Diameter of a Grained Structure with Medium
Undulation
The surface of a support is photographed at a magnification of
2,000 from right above with an electron microscope. Next, in an
electron micrograph obtained, at least 50 pits of the grained
structure with medium undulation (pit of medium undulation) in
which circumferences of the pits are annularly connected are
extracted, the aperture diameters are determined by reading the
diameters of the pits, and an average aperture diameter is
calculated. In the case of a structure in which a grained structure
with large undulation is superimposed also, measurement is made in
the same method as in the above.
In addition, in order to suppress dispersion among measurements, an
equivalent circle diameter may be measured with a commercial image
analysis software. In this case, the aforementioned electron
micrograph is digitized by being scanned with a scanner, and an
equivalent circle diameter is found after it is converted into
binary values with the software.
The measurement results by the inventors showed that a visual
measurement and that of digitization were almost the same value. In
the case of a structure in which the grained structure with large
undulation are superimposed, a similar result was obtained.
(2) Average Aperture Diameter of a Grained Structure with Small
Undulation
The surface of a support for a lithographic printing plate is
photographed at a magnification of 50,000 from right above with a
high resolution scanning electron microscope (SEM). In a SEM
micrograph obtained, at least 50 pits of the grained structure with
small undulation (pit of small undulation) are extracted, the
aperture diameter is determined by reading the diameters of the
pits and an average aperture diameter is calculated.
(3) Average of Ratio of Depth with Respect to the Aperture Diameter
of the Grained Structure with Small Undulation
The average of ratio of depth with respect to aperture diameter of
the grained structure with small undulation is obtained as follows.
A broken-out section of a support is photographed at a
magnification of 50,000 with a high resolution SEM. In a SEM
micrograph obtained, at least 20 pits of small undulation are
extracted, the ratios are obtained by reading the aperture
diameters and depths, and an average ratio is calculated.
(4) Average Wavelength of a Grained Structure with Large
Undulation
A two-dimensional roughness measurement is performed with a stylus
type surface roughness gauge, mean spacing of peaks S.sub.m
specified in ISO4287 is measured five times, and its mean value is
determined to be an average wavelength.
A support for a lithographic printing plate according to the second
aspect of the present invention is characterized in that each of
R.sub.a, .DELTA.S, a30 and a60 obtained from three-dimensional data
taken by measuring 50 .mu.m.quadrature. area on a surface at
512.times.512 points with an atomic force microscope meets the
following requirements (i) to (iv):
TABLE-US-00001 (i) R.sub.a: 0.45 .mu.m or more (ii) .DELTA.S: 30%
or more (iii) a30: 55% or more (iv) a60: 10% or less.
As to be described later, R.sub.a indicates a surface roughness
obtained by removing components of wavelength 2 .mu.m or longer
from the aforementioned three-dimensional data. Specifically,
surface roughness R.sub.a indicates the states of asperities on the
support surface.
If this R.sub.a is too small, the surface becomes smooth, whereby
light easily reflect regularly. As a result, when fountain solution
is supplied to the surface of non-image areas in a lithographic
printing plate at the time of printing, it is difficult to visually
inspect and control an amount of the supplied fountain solution
since the surface of a printing plate easily dazzles.
According to the second aspect of the present invention, R.sub.a is
set to be relatively large in order to allow easy visual inspection
of an amount of the fountain solution supplied to the surface of
the printing plate at the time of printing, that is, to make
inspectability of the lithographic printing plate excellent. In the
second aspect of the present invention, R.sub.a is 0.45 .mu.m or
more, and preferably 0.50 .mu.m or more.
As to be described later in detail, .DELTA.S is found by the
following equation from an actual area S.sub.x found by the
approximation three-point method from the aforementioned
three-dimensional data and a geometrically measured area (apparent
area) S.sub.0: .DELTA.S=(S.sub.x-S.sub.0)/S.sub.0.times.100(%)
The surface area ratio .DELTA.S is a factor that indicates an
extent of increase of the actual area S.sub.x due to graining
treatment with respect to the geometrically measured area S.sub.o.
If .DELTA.S becomes larger, a contact area with an image recording
layer becomes larger, resulting in improvement of press life. It is
effective to provide a large number of small asperities on the
surface in order to increase .DELTA.S. The methods of providing a
large number of small asperities on the surface preferably include
electrolytic graining treatment with an electrolyte composed mainly
by hydrochloric acid, and electrolytic graining treatment with an
electrolyte composed mainly by highly concentrated nitric acid at a
high temperature. Although .DELTA.S is also increased by mechanical
graining treatment or electrolytic graining treatment with an
electrolyte mainly composed of ordinary nitric acid, the extent of
the increase is small.
According to the second aspect of the present invention, .DELTA.S
is 30% or more, and preferably 40% or more.
As to be described later, a30 and a60 indicate an area ratio of an
area of gradient 30.degree. or more and an area of gradient
60.degree. or more, respectively, obtained after removing
components of wavelength 2 .mu.m or longer from the aforementioned
three-dimensional data.
Steepness is a factor that indicates an extent of sharpness of a
fine shape on the support surface. Specifically, steepness
indicates a ratio of an area having a slant with a given angle or
larger with respect to an apparent area in asperities on the
support surface. The inventors have variously studied steepness to
find out that steepness is correlated with contact characteristics
between an image recording layer and a support (i.e. press life),
and with ink attachment characteristics in non-image areas (i.e.
scum resistance). Particularly, they have found out that press life
and scum resistance can be achieved at a high level by balancing
two of the steepness based on the specified angles of 30.degree.
and 60.degree..
That is, it is preferable to have a larger area ratio (steepness)
a30 of a more gentle slope with gradient 30.degree. or more, in
order to give an excellent contact characteristics between the
image recording layer and the support, and to improve press life.
In addition, a larger a30 is preferable also in order to improve
both water receptivity of the non-image areas of the lithographic
printing plate and thus scum resistance. According to the second
aspect of the present invention, a30 is 55% or more, and preferably
60% or more.
On the other hand, it is preferable to have a smaller area ratio
(steepness) a60 of a steeper slope with gradient 60.degree. or
more, in order to suppress ink attachment in the non-image areas to
improve scum resistance. According to the second aspect of the
present invention, a60 is 10% or less, and preferably 7% or
less.
In a support for a lithographic printing plate according to the
second aspect of the present invention, methods of finding R.sub.a,
.DELTA.S, a30 and a60 are as follows.
(5) Measurement of Surface Shape with an Atomic Force
Microscope
According to the second aspect of the present invention, in order
to find R.sub.a, .DELTA.S, a30 and a60, surface shapes are measured
with an atomic force microscope (AFM) and three-dimensional data
are then taken.
Measurement can be performed on the following conditions, for
example. That is, 1 cm-square of the support for a lithographic
printing plate is cut off, the piece is set on a horizontal sample
bench on a piezo scanner, a cantilever is moved closer to the
surface of the sample, and when the cantilever reaches an area
where an atomic force functions, the sample is scanned in XY
directions. While scanning, asperities of the sample are captured
as piezo displacement in Z direction. A piezo scanner capable of
scanning 150 .mu.m in XY directions and 10 .mu.m in Z direction,
respectively, should be used. A cantilever with resonance frequency
of 120 to 150 kHz, and spring constant of 12 to 20 N/m (e.g.,
S1-DF20 made by NANOPROBE Inc.) should be used, and measurement is
performed in DFM mode (Dynamic Force Mode). A minor tilting of the
sample is corrected by least square approximation method of the
three-dimensional data obtained to find a reference plane.
At the time of measurement, a surface in 50 .mu.m.quadrature. area
is measured at 512.times.512 points. The resolution in XY
directions should be 1.9 .mu.m, the resolution in Z direction
should be 1 nm, and scanning rate should be 60 .mu.m/sec.
(6) Correction of Three-dimensional Data
While in the calculation of .DELTA.S, the three-dimensional data
found in (5) mentioned above is used as it stands, in calculation
of R.sub.a, a30 and a60, a data that is corrected by removing
components of wavelength 2 .mu.m or longer from the
three-dimensional data taken in (5) mentioned above is employed.
This correction can remove noises generated by a probe hitting the
edge portion of a convex portion and jumping, or by a portion other
than an edge of the probe contacting the wall surface of a deep
concave portion when a surface with deep asperities as in a support
for a lithographic printing plate is scanned with a probe of
AFM.
The correction is performed by performing the fast Fourier
transform of the three-dimensional data taken in (5) mentioned
above to find frequency distribution, and performing inverse
Fourier transform after removing components of wavelength 2 .mu.m
or longer.
(7) Calculation of Each Factor
(i) R.sub.a
Surface roughness R.sub.a is calculated by the following equation
using the three-dimensional data (f (x, y)) obtained after a
correction is performed in (6) mentioned above.
.times..intg..times..intg..times..function..times..times.dd
##EQU00001##
In the equation, each of L.sub.x and L.sub.y indicates the length
of a side in x direction and y direction of a measured area
(rectangle) and their relation is that L.sub.x=L.sub.y=50 .mu.m in
the second aspect according to the present invention. In addition,
S.sub.o is geometrically measured area and is found by an equation
that S.sub.o=L.sub.x.times.L.sub.y.
(ii) .DELTA.S
Adjacent three points are extracted using the three-dimensional
data (f (x, y)) found in (5) mentioned above, and the total of
areas of fine triangles formed by the three points is found, which
is determined to be actual area S.sub.x. Surface area ratio
.DELTA.S is found by the following equation from the obtained
actual area S.sub.x and geometrically measured area S.sub.0:
.DELTA.S=(S.sub.x-S.sub.0)/S.sub.0.times.100(%)
(iii) a30 and a60
Using the three-dimensional data (f (x, y)) obtained by correction
in (6) mentioned above, an angle made between a reference plane and
a fine triangle formed by the three points constituted by each
reference point and adjacent two points in predetermined directions
(for example, rightwards and downwards) is calculated, for each
reference point. The number of reference points at which a gradient
of the fine triangle is 30.degree. or more (in the case of a30) or
60.degree. or more (in the case of a60) is divided by the number of
all reference points (herein, the number of all reference points is
511.times.511 points, that is obtained by subtracting the number of
points which do not have adjacent two points in the predetermined
directions from 512.times.512 points, that is, the number of all
data). Accordingly, an area ratio a30 of a portion of gradient
30.degree. or more and an area ratio a60 of a portion of gradient
60.degree. or more are calculated.
One of the particularly preferred aspects according to the present
invention is a support for a lithographic printing plate that
satisfies both the first aspect and the second aspect according to
the present invention.
<Surface Treatment>
A support for a lithographic printing plate according to the
present invention is one that, by performing surface treatment on
an aluminum plate to be described later, the aforementioned surface
grain shape on a surface is formed on the surface of the aluminum
plate. While the support for a lithographic printing plate
according to the present invention is obtained by performing at
least graining treatment on an aluminum plate, the producing method
of the support is not particularly limited and may include various
processes other than graining treatment.
As typical methods of forming the aforementioned grain shape on a
surface, the following methods will be explained:
a method by sequentially performing mechanical graining treatment,
alkali etching treatment, desmutting treatment with an acid, and
electrochemical graining treatment with an electrolyte on an
aluminum plate;
a method by performing, for several times, mechanical graining
treatment, alkali etching treatment, desmutting treatment with an
acid, and electrochemical graining treatment with an electrolyte on
an aluminum plate;
a method by sequentially performing alkali etching treatment,
desmutting treatment with an acid, and electrochemical graining
treatment with an electrolyte on an aluminum plate; and
a method by performing, for several times, alkali etching
treatment, desmutting treatment with an acid, and electrochemical
graining treatment with an electrolyte on an aluminum plate.
However, according to the present invention, the method is not
limited to the above. In these methods, alkali etching treatment
and desmutting treatment may be further performed after the
electrochemical graining treatment as above is performed.
In addition, graining treatment preferably used so as to allow each
of R.sub.a, .DELTA.S, a30 and a60 that are the factors to indicate
surface shapes according to the second aspect of the present
invention to satisfy specified conditions includes a method by
sequentially performing mechanical graining treatment,
electrochemical graining treatment with an electrolyte mainly
composed of nitric acid, and electrochemical graining treatment
with an electrolyte mainly composed of hydrochloric acid, although
it depends on conditions of other treatment (alkali etching
treatment or the like). In addition, the graining treatment also
includes a method by performing only electrochemical graining
treatment in which the total amount of electricity involved in
anodizing reaction is increased with an electrolyte mainly composed
of hydrochloric acid.
According to the first aspect and the second aspect of the present
invention, one of particularly preferable methods is a method by
sequentially performing, on an aluminum plate, mechanical graining
treatment, alkali etching treatment, desmutting treatment with an
acid, electrochemical graining treatment with an electrolyte
containing nitric acid, alkali etching treatment, desmutting
treatment with an acid, electrochemical graining treatment with an
electrolyte containing hydrochloric acid, alkali etching treatment,
and desmutting treatment with an acid.
A support surface for a lithographic printing plate according to
the first aspect of the present invention obtained in these methods
has a structure in which two or more different profile cycles of
asperities are superimposed on the surface thereof, and is
excellent in both scum resistance and press life when a
lithographic printing plate is made therefrom.
A support for a lithographic printing plate according to the second
aspect of the present invention obtained by these methods and in
which each of the aforementioned factors indicating a surface shape
satisfies the specified requirement, is excellent in both scum
resistance and press life when a lithographic printing plate is
made therefrom.
Hereafter, each process of surface treatment will be explained in
detail.
<Mechanical Graining Treatment>
Mechanical graining treatment is effective means for graining
treatment since it is capable of forming a surface with average
wavelength 5 to 100 .mu.m asperities at a lower cost than
electrochemical graining treatment.
Mechanical graining treatment that can be used includes wire brush
graining treatment by scratching an aluminum plate surface with
metal wire, ball graining treatment by performing graining on an
aluminum plate surface with an abrasive ball and an abrasive agent,
and brush graining treatment by performing graining on a surface
with a nylon brush and an abrasive agent as described in JP
6-135175 A and JP 50-40047 B.
In addition, a transfer method in which a surface with asperities
is pressed onto an aluminum plate can be also employed. That is,
applicable methods include those described in JP 55-74898 A, JP
60-36195 A and JP 60-203496 A, as well as a method described in JP
6-55871 A characterized by performing transfer several times, and a
method described in JP 6-024168 A characterized in that the surface
is elastic.
It is also possible to use a method by repeatedly performing
transfer using a transfer roller on which fine asperities are
etched with electric discharge machining, shot blast, laser, plasma
etching or the like, and a method in which a surface with
asperities on which fine particles are applied is allowed to
contact with an aluminum plate, pressure is applied on that several
times, and transfer of the asperity pattern equivalent to average
diameter of fine particles is repeatedly performed on an aluminum
plate several times. A method of providing fine asperities to a
transfer roll includes methods known to the public, as described in
JP 3-8635 A, JP 3-66404 A, JP 63-65017 A or the like. In addition,
fine grooves may be engraved on the surface of the transfer roll
from two directions with a dice, a turning tool, a laser or the
like to form square asperities on the surface. Also, publicly known
etching treatment or the like may be performed on the surface of
the transfer roll such that the formed square asperities become
round.
In addition, hardening, hard chrome plating or the like may be
performed to increase hardness of a surface.
Moreover, mechanical graining treatment may include methods as
described in JP 61-162351 A, JP 63-104889 A or the like.
In the present invention, each method as above may be used in
combination with others, taking productivity or the like into
consideration. It is preferable that these mechanical graining
treatments are performed before electrochemical graining
treatment.
Hereafter, brush graining treatment preferably used as mechanical
graining treatment will be explained.
Brush graining treatment generally uses a roller-like brush in
which a lot of synthetic resin brushes made of synthetic resin such
as nylon (trademark), polypropylene and PVC resin are implanted on
the surface of a cylindrical drum, and treatment is performed by
scrubbing one or both of the surfaces of the aluminum plate while
spraying a slurry containing an abrasive over a rotating
roller-like brush. An abrasive roller on which an abrasive layer is
provided may be also used in place of the roller-like brush and a
slurry.
When a roller-like brush is used, bending elastic modulus is
preferably 10,000 to 40,000 kg/cm.sup.2, more preferably 15,000 to
35,000 kg/cm.sup.2, and a treatment should use a brush with bristle
elasticity of, preferably 500 g or less, more preferably 400 g or
less. The diameter of the bristle is generally 0.2 to 0.9 mm. While
the length of the bristle can be appropriately determined depending
on the outer diameter of the roller-like brush and the diameter of
the drum, it is generally 10 to 100 mm.
As to an abrasive, a publicly known one may be used. Abrasives that
can be used include pumice, silica sand, aluminum hydroxide,
alumina powder, silicon carbide, silicon nitride, volcanic ash,
carborundum, emery, and mixtures thereof. Pumice and silica sand
are preferable among them. Silica sand is particularly preferable
because of excellent graining efficiency since it is harder than
pumice and is not easily broken compared to pumice.
A preferable average particle diameter of the abrasive is 3 to 50
.mu.m, and more preferably 6 to 45 .mu.m, from the viewpoint of
excellent graining efficiency and that graining pitch can be
narrowed.
An abrasive is, for example, suspended in water and used as a
slurry. Beside abrasives, thickener, dispersant (for example,
surfactant), antiseptic agent or the like may be contained in the
slurry. It is preferable that the specific gravity of a slurry is
0.5 to 2.
As an apparatus suitable for mechanical graining treatment, for
example, includes an apparatus as described in JP 50-40047 B.
<Electrochemical Graining Treatment>
Electrochemical graining treatment may use en electrolyte used for
electrochemical graining treatment with an ordinary alternating
current. Particularly, a structure of asperities unique to the
present invention may be formed on a surface by using an
electrolyte mainly composed of hydrochloric acid or nitric
acid.
As electrolytic graining according to the present invention, it is
preferable that the first and second electrolytic treatments are
performed in an acid solution in alternating corrugated current
before and after the cathode electrolytic treatment. Hydrogen gas
is generated on the surface of an aluminum plate to produce smut by
cathode electrolytic treatment, thereby creating an even surface
condition. This allows the even graining treatment to be performed
at the time of electrolytic treatment by the subsequent alternating
corrugated current.
This electrolytic graining treatment can follow the electrochemical
graining treatment (electrolytic graining treatment) as described
in JP 48-28123 B and GB 896,563, for example. Although this
electrolytic graining treatment uses sine waveform alternating
current, a special waveform may be used as described in JP 52-58602
A. In addition, a waveform as described in JP 3-79799 A can be also
used. Moreover; the methods as described in JP 55-158298 A, JP
56-28898 A, JP 52-58602 A, JP 52-152302 A, JP 54-85802 A, JP
60-190392 A, JP 58-120531 A, JP 63-176187 A, JP 1-5889 A, JP
1-280590 A, JP 1-118489 A, JP 1-148592 A, JP 1-178496 A, JP
1-188315 A, JP 1-154797 A, JP 2-235794 A, JP 3-260100 A, JP
3-253600 A, JP 4-72079 A, JP 4-72098 A, JP 3-267400 A and JP
1-141094 A may also be used. In addition, besides the
aforementioned, it is also possible to perform electrolysis using a
special frequency alternating current proposed as a method for
producing an electrolytic capacitor. It is described for example in
U.S. Pat. Nos. 4,276,129 and 4,676,879.
While an electrolytic bath and power supply are variously proposed,
those as described in U.S. Pat. No. 4,203,637, JP 56-123400 A, JP
57-59770 A, JP 53-12738 A, JP 53-32821 A, JP 53-32822 A, JP
53-32823 A, JP 55-122896 A, JP 55-132884 A, JP 62-127500 A, JP
1-52100 A, JP 1-52098 A, JP 60-67700 A, JP 1-230800 A, JP 3-257199
A or the like can be used.
In addition, those as described in JP 52-58602 A, JP 52-152302 A,
JP 53-12738 A, JP 53-12739 A, JP 53-32821 A, JP 53-32822 A, JP
53-32833 A, JP 53-32824 A, JP 53-32825 A, JP 54-85802 A, JP
55-122896 A, JP 55-132884 A, JP 48-28123 B, JP 51-7081 B, JP
52-133838 A, JP 52-133840 A, JP 52-133844 A, JP 52-133845 A, JP
53-149135 A, JP 54-146234 A or the like can be used.
As an acid solution that is an electrolyte, in addition to nitric
acid and hydrochloric acid, the electrolytes as described in U.S.
Pat. Nos. 4,671,859, 4,661,219, 4,618,405, 4,600,482, 4,566,960,
4,566,958, 4,566,959, 4,416,972, 4,374,710, 4,336,113 and 4,184,932
or the like can be used.
The concentration of an acid solution should preferably be 0.5 to
2.5 wt %, and it should be particularly preferably 0.7 to 2.0 wt %,
taking the use for desmutting treatment into account. In addition,
the temperature of a solution should preferably be 20 to 80.degree.
C., and should more preferably be 30 to 60.degree. C.
An aqueous solution mainly composed of hydrochloric acid or nitric
acid can be used in such a manner that at least one of nitrates
having nitrate ion such as aluminum nitrate, sodium nitrate and
ammonium nitrate or chlorides having chlorine ion such as aluminum
chloride, sodium chloride and ammonium chloride is added in a range
from 1 g/L to a saturation point to hydrochloric acid or nitric
acid aqueous solution of the concentration 1 to 100 g/L. In
addition, metals contained in aluminum alloys such as iron, copper;
manganese, nickel, titanium, magnesium and silicon may be dissolved
in the aqueous solution mainly composed of hydrochloric acid or
nitric acid. It is preferable that a solution in which aluminum
chloride, aluminum nitrate and the like are added to an aqueous
solution containing hydrochloric acid or nitric acid of the
concentration of 0.5 to 2 wt % so as to allow aluminum ion of 3 to
50 g/L to be contained is used.
In addition, it is possible to perform the even graining also on an
aluminum plate containing a large amount of copper by adding a
compound capable of forming a complex with copper and using it.
Compounds capable of forming a complex with copper include ammonia;
amines obtained by substituting hydrogen atom in ammonia by
hydrocarbon group (aliphatic and aromatic, or the like) or the
like, such as methylamine, ethylamine, dimethylamine, diethylamine,
trimethylamine, cyclohexylamine, triethanolamine,
triisopropanolamine, EDTA (ethylenediaminetetraacetic acid); metal
carbonates such as sodium carbonate, potassium carbonate and
potassium hydrogencarbonate. Ammonium salts such as ammonium
nitrate, ammonium chloride, ammonium sulfate, ammonium phosphate
and ammonium carbonate are also included.
The temperature should preferably be 10 to 60.degree. C., and
should more preferably be 20 to 50.degree. C.
Alternating current power supply wave used for electrochemical
graining treatment is not particularly limited and sine wave,
square wave, trapezoidal wave, triangle wave or the like are used.
Square wave or trapezoidal wave is preferable, and trapezoidal wave
is particularly preferable. Trapezoidal wave is one as shown in
FIG. 2. It is preferable that with this trapezoidal wave, a time
required for the current to reach a peak from zero (TP) is 1 to 3
msec. If it is less than 1 msec, non-uniformity in treatment called
chatter mark is easily generated in a direction perpendicular to a
traveling direction of an aluminum plate. If TP exceeds 3 msec,
particularly when nitric acid electrolyte is used, an aluminum
plate is easily affected by trace components in an electrolyte
represented by ammonium ion or the like that spontaneously increase
in electrochemical graining treatment, thus the even graining is
not easily performed. As a result, scum resistance is likely to
deteriorate when a lithographic printing plate is prepared.
Trapezoidal wave alternating current with a duty ratio of 1:2 to
2:1 is usable, and duty ratio should preferably be 1:1 in an
indirect power supplying system dispensing with a conductor roll
for aluminum as described in JP 5-195300 A.
While trapezoidal wave alternating current with a frequency of 0.1
to 120 Hz is usable, frequency should preferably be 50 to 70 Hz in
terms of equipment. If it is lower than 50 Hz, the carbon electrode
of a main electrode is easily dissolved, and if it is higher than
70 Hz, it is easily affected by the components of inductance in a
power supply circuit, thus an electric power cost increases.
One or more alternating current power supplies can be connected to
an electrolytic bath. It is preferable that, as shown in FIG. 3, an
auxiliary anode is installed and a part of alternating current is
shunted, for the purpose of controlling the current ratio at the
anode and the cathode of alternating current applied to an aluminum
plate opposite to the main electrode so as to perform the even
graining and dissolve carbon in the main electrode. In FIG. 3, a
reference numeral 11 denotes an aluminum plate, 12 denotes a radial
drum roller, 13a and 13b denote main electrodes, 14 denotes an
electrolyte, 15 denotes an electrolyte feed port, 16 denotes a
slit, 17 denotes an electrolyte path, 18 denotes an auxiliary
anode, 19a and 19b denote thyristors, 20 denotes an alternating
current power supply, 40 denotes a main electrolytic bath, and 50
denotes an auxiliary anodizing bath. By shunting a part of a
current value to an auxiliary anode provided in a bath different
from the two main electrode baths in the two main electrodes as
direct current via a rectifying device or a switching device, the
ratio of a current value used for an anodizing reaction with
respect to a current value used for a cathodic reaction reacting on
the aluminum plate opposite to the main electrode can be
controlled. It is preferable that the ratio of amount of
electricity (amount of electricity at cathode/amount of electricity
at anode) used for an anodizing reaction and a cathodic reaction on
the aluminum plate opposite to the main electrode is 0.3 to
0.95.
While an electrolytic bath used for a publicly known surface
treatment such as a vertical type, a flat type and a radial type is
usable, a radial type electrolytic bath as described in JP 5-195300
A is particularly preferable. The direction of travel of an
electrolyte which passes through the electrolytic bath may be
parallel with or perpendicular to that of an aluminum web.
(Electrolysis with Nitric Acid)
A pit with average aperture diameter of 0.5 to 5 .mu.m can be
formed by performing electrochemical graining treatment using an
electrolyte mainly composed of nitric acid. If amount of
electricity is, however, relatively large, an electrolytic reaction
concentrates to produce a honeycomb pit with an aperture diameter
of even more than 5 .mu.m.
In order to obtain graining like this, the total amount of
electricity used for the anodizing reaction of the aluminum plate
at a time when an electrolytic reaction is completed should
preferably be 1 to 1,000 C/dm.sup.2, and should more preferably be
50 to 300 C/dm.sup.2. It is preferable that current density is 20
to 100 A/dm.sup.2 in this case.
If an electrolyte containing nitric acid of a high concentration or
a high temperature is used, a grained structure with small
undulation of average aperture diameter of 0.2 .mu.m or less can be
also formed.
(Electrolysis with Hydrochloric Acid)
Since hydrochloric acid per se has a strong aluminum solvency, it
is possible to form micro asperities on its surface by merely
applying a little electrolysis thereon. These micro asperities are
of average aperture diameter 0.01 to 0.2 .mu.m and are evenly
formed on the entire surface of the aluminum plate. In order to
obtain graining like this, the total amount of electricity used for
the anodizing reaction of an aluminum plate at a time when an
electrolytic reaction is completed should preferably be 1 to 100
C/dm.sup.2, more preferably be 20 to 70 C/dm.sup.2. It is
preferable that current density is 20 to 50 A/dm.sup.2 in this
case.
It is also possible to simultaneously form a crater-like large
undulation by increasing the total amount of electricity used for
an anodizing reaction to 400 to 1,000 C/dm.sup.2 in electrochemical
graining treatment with an electrolyte mainly composed of
hydrochloric acid like this. In this case, micro asperities of
average aperture diameter 0.01 to 0.4 .mu.m are formed on the
entire surface, being superimposed on a crater-like large
undulation of average aperture diameter 10 to 30 .mu.m. Therefore,
since a grained structure with medium undulation of average
aperture diameter 0.5 to 5 .mu.m can not be superimposed thereon in
this case, the graining of a surface that is the characteristic of
the first aspect according to the present invention can not be
produced. It might be possible, however, that each factor of the
second aspect according to the present invention satisfies the
specified conditions, respectively.
It is preferable that in the present invention, electrolytic
graining treatment with an electrolyte mainly composed of nitric
acid (electrolysis with nitric acid) as mentioned above is
performed as the first electrolytic graining treatment, and
electrolytic graining treatment with an electrolyte mainly composed
of hydrochloric acid (electrolysis with hydrochloric acid) as
mentioned above is performed as the second electrochemical graining
treatment. That is, the present invention also provides a method of
producing a support for a lithographic printing plate by
sequentially performing electrolysis with nitric acid and
electrolysis with hydrochloric acid on at least an aluminum plate
as graining treatment, and further performing anodizing
treatment.
It is preferable that cathode electrolytic treatment is performed
on the aluminum plate between the first and the second electrolytic
graining treatments in electrolyte containing nitric acid,
hydrochloric acid or the like, as mentioned above. This cathode
electrolytic treatment allows smut to be produced on the surface of
the aluminum plate and hydrogen gas to be generated, and thus
electrolytic graining treatment can be more evenly performed. This
cathodic electrolytic treatment is performed with cathodic amount
of electricity preferably 3 to 80 C/dm.sup.2 in an acid solution,
and more preferably 5 to 30 C/dm.sup.2. If cathodic amount of
electricity is less than 3 C/dm.sup.2, an amount of attached smut
may be insufficient, and if it exceeds 80 C/dm.sup.2, an amount of
attached smut may be too excessive. Both cases are not preferable.
In addition, the cathodic electrolytic treatment may use the same
electrolytes used for the first and second electrolytic graining
treatments, or a different electrolyte.
<Alkali Etching Treatment>
Alkali etching treatment is a treatment that dissolves a surface
layer of the aforementioned aluminum plate by allowing the aluminum
plate to contact with an alkali solution.
Alkali etching treatment performed before electrolytic graining
treatment is performed to remove rolling oil, dirt, naturally
oxidized layer or the like on the surface of the aluminum plate
(rolled aluminum) if mechanical graining treatment is not performed
thereon, and is performed to dissolve edge portions of asperities
generated by mechanical graining treatment to change steeper
asperities on the surface to a smoother surge surface if mechanical
graining treatment has been already performed.
If mechanical graining treatment is not performed before alkali
etching treatment, an amount of etching should preferably be 0.1 to
10 g/m.sup.2, and more preferably be 1 to 5 g/m.sup.2. If an amount
of etching is less than 0.1 g/m.sup.2, pits can not be formed
evenly to produce non-uniformity in electrolytic graining treatment
to be performed later since rolling oil, dirt, naturally oxidized
layer or the like may be left on the surface of a plate. On the
other hand, if an amount of etching is 1 to 10 g/m.sup.2, rolling
oil, dirt, naturally oxidized layer and the like are fully removed
from the surface of a plate. If an amount of etching exceeds that
range, it is less economical.
If mechanical graining treatment is performed before alkali etching
treatment, an amount of etching should preferably be 3 to 20
g/m.sup.2, and more preferably be 5 to 15 g/m.sup.2. If an amount
of etching is less than 3 g/m.sup.2, the asperities formed by
mechanical graining treatment or the like may not be sometimes
smoothed, and pits can not be evenly formed in electrolytic
treatment to be performed later. In addition, dirt may deteriorate
during printing. On the other hand, if an amount of etching exceeds
20 g/m.sup.2, asperities structure will disappear.
Alkali etching treatment just after electrolytic graining treatment
is performed to dissolve smut produced in an acid electrolyte and
to dissolve edge portions of pits formed by electrolytic graining
treatment.
An optimum amount of etching varies since a pit formed by
electrolytic graining treatment varies according to the kind of an
electrolyte. However, it is preferable that an amount of etching in
alkali etching treatment after electrolytic graining treatment is
0.1 to 5 g/m.sup.2. If a nitric acid electrolyte is used, it is
necessary to set an amount of etching to a greater amount than that
of the case a hydrochloric acid electrolyte is used.
If electrolytic graining treatment is performed several times,
alkali etching treatment can be performed after each electrolytic
graining treatment as required.
Alkali used for an alkali solution includes, for example, caustic
alkali and alkali metal salts. More specifically, it includes
sodium hydroxide and potassium hydroxide. In addition, it includes
silicates of alkali metals such as sodium metasilicate, sodium
silicate, potassium metasilicate, potassium silicate; carbonates of
alkali metals such as sodium carbonate and potassium carbonate;
aluminates of alkali metals such as sodium aluminate and potassium
aluminate; aldonates of alkali metals such as sodium gluconates and
potassium gluconates; hydrogenphosphates of alkali metals such as
disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium
dihydrogenphosphate and potassium dihydrogenphosphate. Among them a
caustic alkali solution and a solution containing both a caustic
alkali and aluminate of alkali metal are preferable from a
viewpoint that the rate of etching is fast and costs are lower.
Particularly, an aqueous solution of sodium hydroxide is
preferable.
The concentration of an alkali solution can be determined in
accordance with an amount of etching, and it should preferably be 1
to 50 wt %, more preferably be 10 to 35 wt %. If aluminum ion is
dissolved in an alkali aqueous solution, the concentration of
aluminum ion should preferably be 0.01 to 10 wt %, more preferably
be 3 to 8 wt %. It is preferable that the temperature of an alkali
aqueous solution is 20 to 90.degree. C., and treatment time is 1 to
120 seconds.
Methods of allowing an aluminum plate to contact with an alkali
solution include, for example, a method by allowing an aluminum
plate to pass through a bath containing an alkali solution, a
method by allowing an aluminum plate to be immersed in a bath
containing an alkali solution, and a method by spraying an alkali
solution over the surface of an aluminum plate.
<Desmutting Treatment>
After electrolytic graining treatment or alkali etching treatment
is performed, pickling (desmutting treatment) is performed to
remove dirt (smut) left on the surface of a plate. Acids that are
used include nitric acid, sulfuric acid, phosphoric acid, chromic
acid, hydrofluoric acid, borofluoric acid or the like.
The desmutting treatment is performed by allowing the aluminum
plate to contact with an acid solution of concentration 0.5 to 30
wt %o of hydrochloric acid, nitric acid, sulfuric acid or the like
(aluminum ion 0.01 to 5 wt % contained). A method of allowing an
aluminum plate to contact with an acid solution include, for
example, a method by allowing an aluminum plate to pass through a
bath containing an acid solution, a method by allowing an aluminum
plate to be immersed in a bath containing an acid solution, and a
method by spraying an acid solution over the surface of an aluminum
plate.
In desmutting treatment, an acid solution that can be used includes
a wastewater of an aqueous solution mainly containing nitric acid
or an aqueous solution mainly containing hydrochloric acid
discharged in the electrolytic treatment described above, or a
wastewater of an aqueous solution mainly containing sulfuric acid
discharged in anodizing treatment described later.
It is preferable that a solution temperature of desmutting is 25 to
90.degree. C. It is preferable that a treatment time is 1 to 180
seconds. Aluminum and aluminum alloy components may be dissolved in
an acid solution used for desmutting treatment.
<Formation of Water Receptive Layer>
It is preferable that an aluminum plate on which graining treatment
and, as required, other treatments are performed as mentioned above
is provided with a water receptive layer of low thermal
conductivity.
The diffusion of a heat generated by the exposure with a laser beam
into a support can be suppressed by setting the thermal
conductivity in the layer thickness direction of a water receptive
layer at 0.05 to 0.5 W/(mK). Since the lower the thermal
conductivity is, the higher the suppressing effect of thermal
diffusion is, the thermal conductivity should more preferably be
0.08 to 0.3 W/(mK) and, particularly preferably, 0.2 W/(mK) or
less.
By providing a layer of low thermal conductivity like this, in a
presensitized plate called a heat mode type which forms an image
utilizing a heat, a sensitivity increases at the time of exposure.
No layers are left in a case of a positive type, and image
formability is improved in a case of a negative type.
Hereafter, thermal conductivity in the layer thickness direction of
a water receptive layer as specified in the third aspect according
to the present invention.
Various methods of measuring the thermal conductivity of a thin
layer have been reported to date. In 1986, Ono et al. reported the
thermal conductivity in the direction of plane of a thin layer by
use of a thermograph. In addition, there is also reported a trial
that an alternating current heating method is applied to measure
thermal properties of a thin layer. While the origin of alternating
current heating method can trace back to a report in 1863, in
recent years, various measurement methods have been proposed due to
development of heating by laser and combinations with Fourier
transform. An equipment with laser angstrom method is actually
commercialized. Each of these methods finds the thermal
conductivity of a direction in plane (inplane direction).
However, a thermal diffusion in a depth direction is rather a vital
factor when considering the thermal conduction of a thin layer. As
variously reported, it is said that the thermal conductivity of a
thin layer is not isotropic, and particularly in a case like the
present invention, it is extremely important to directly measure
the thermal conductivity in the layer thickness direction. As a
trial to measure thermophysical properties of a layer thickness
direction of a thin layer from the view point like this, a method
using a thermocomparator is reported in a treatise published by
Lambropoulos et al. (J. Appl. Phys., 66 (9)(1 Nov. 1989)) and a
treatise published by Henager et al. (APPLIED OPTICS, Vol. 32, No.1
(1 Jan. 1993)). In addition, Hashimoto et al. recently reported a
method of measuring thermal diffusivity of a thin polymer layer by
an analysis using temperature wave for Fourier transform thermal
analysis (Netsu Sokutei, 27 (3) (2000)).
The thermal conductivity in a layer thickness direction of a water
receptive layer as defined in the present invention is measured
with a method using the aforementioned thermocomparator. The method
is concretely described below. The basic principle of the method is
described in detail in the treatise published by Lambropoulos et
al. and the treatise published by Henager et al. as aforementioned.
In addition, equipment used for the method is not limited to the
following equipment.
FIG. 5 is a schematic view of a thermocomparator 530 that can be
used to measure the thermal conductivity in a layer thickness
direction of the water receptive layer of a support for a
lithographic printing plate according to the present invention. As
shown in FIG. 5, reference numeral 530 denotes a thermocomparator,
reference numeral 531 denotes a chip, reference numeral 532 denotes
a reservoir, reference numeral 533 denotes an electric heater,
reference numeral 534 denotes a heating jacket, reference numeral
535 denotes a thermocouple, reference numeral 536 denotes a heat
sink, reference numeral 537 denotes a layer, reference numeral 538
denotes a metal substrate, reference numeral 539 denotes a contact
thermometer, reference numeral 540 denotes a chip tip thermograph,
reference numeral 541 denotes heat sink thermograph, and reference
numeral 542 denotes a reservoir thermograph.
In a method using a thermocomparator, a measurement is largely
affected by a contact area with a thin layer and the condition
(i.e. roughness) of a contact surface. For that reason, it is
essential that the tip of thermocomparator 530 that contacts with
the thin layer should be as fine as possible. For example, a chip
(wire) 531 having a fine tip of radius r.sub.1=0.2 mm made of
oxygen-free copper is used.
This chip 531 is fixed in place at the center of the reservoir 532
made of constantan and a heating jacket 534 made of oxygen-free
copper having an electric heater 533 is fixed in place around the
reservoir 532. If this heating jacket 534 is heated by the electric
heater 533 and reservoir 532 is so controlled as to be at
60.+-.1.degree. C. while an output of the thermocouple 535 mounted
inside the reservoir 532 is fed back, the chip 531 is heated to
60.+-.1.degree. C. On the other hand, a heat sink 536 made of
oxygen-free copper of radius 10 cm and thickness 10 mm is prepared
and the metal substrate 538 having the layer 537 to be measured is
mounted on the heat sink 536. The surface temperature of the heat
sink 536 is measured with the contact thermometer 539.
After the thermocomparator 530 is set up like this, a tip of the
heated chip 531 is allowed to contact with the surface of layer
537. The thermocomparator 530 is, for example, mounted at the tip
of a dynamic microhardness meter in place of an indenter so as to
be driven up and down, and is allowed to be pressed until the chip
531 hits the surface of the layer 537 and a 0.5 mN load is applied.
This allows variation in a contact area between the layer 537 to be
measured and the chip 531 to be minimized.
If the heated chip 531 is allowed to contact with the layer 537,
the tip temperature of the chip 531 drops but reaches to a
stationary state at a specific constant temperature. This is
because a heat quantity given to the chip 531 via the heating
jacket 534 and the reservoir 532 from the electric heater 533 and a
heat quantity diffused into the heat sink 536 via the metal
substrate 538 from the chip 531 are equilibrated. In this case, the
chip tip thermograph 540 records the tip temperatures of chip, the
heat sink thermograph 541 records the temperature of the heat sink
and the reservoir thermograph 542 records the temperature of the
reservoir, respectively.
The relationship between each temperature as aforementioned and the
thermal conductivity of the layer is described in the following
equation [1]:
.times..times..times..times..times..times..times..times..times..times.
##EQU00002##
Here, the symbols express the following:
T.sub.t: Tip temperature of chip, T.sub.b: Heat sink temperature,
T.sub.r: Reservoir temperature, K.sub.tf: Layer thermal
conductivity, K.sub.1: Thermal conductivity of reservoir, K.sub.2:
Thermal conductivity of chip (in case of oxygen-free copper, 400
W/(mK)), K.sub.4: Thermal conductivity of metal substrate (in case
no layer is provided), r.sub.1: Radius of curvature of tip of chip,
A.sub.2: Contact area between the reservoir and the chip, A.sub.3:
Contact area between the chip and the layer, t: Layer thickness,
t.sub.2: Contact thickness (.apprxeq.0).
The gradient of the equation [1] is found by measuring each
temperature (T.sub.t, T.sub.b, and T.sub.r) while changing the
layer thickness (t) to and plotting them, and the thermal
conductivity of a layer (K.sub.tf) can be found. That is, as is
clear from the equation [1], this gradient is a value that is
determined by reservoir thermal conductivity (K.sub.1), radius of
curvature of tip of chip (r.sub.1), layer thermal conductivity
(K.sub.tf) and contact area (A.sub.3) between the chip and the
layer. Since K.sub.1, r.sub.1 and A.sub.3 are already known values,
a value of K.sub.tf can be found from the gradient.
The inventors have found thermal conductivity of an anodized layer
(Al.sub.2O.sub.3) provided on an aluminum plate with the measuring
method as above. The thermal conductivity of Al.sub.2O.sub.3 found
from the gradient of the graph made from the results of measuring
each temperature of the layer while changing the thickness thereof
is 0.69 W/(mK)). This well agrees with the results as described in
the treatise published by Lambropoulos et al. as aforementioned. In
addition, this result also indicates that the value of thermal
property of the thin layer is different from that of bulk (thermal
conductivity of bulk Al.sub.2O.sub.3 is 28 W/(mK)).
It is preferable to use a method of measuring the thermal
conductivity in a layer thickness direction of a water receptive
layer in a presensitized plate according to the present invention,
because a result without variation for even the surface on which
graining is performed for a lithographic printing plate can be
obtained by using a fine tip of a chip and keeping a pressing load
constant. It is preferable that the value of a thermal conductivity
is found as the average value of values measured at different
several points, for example, at 5 points on a sample.
The thickness of a water receptive layer should preferably be 0.1
.mu.m or more from the view point of scratch resistance and press
life, and more preferably be 0.3 .mu.m or more, and particularly
preferably be 0.6 .mu.m or more. In addition, it should preferably
be 5 .mu.m or less, more preferably be 3 .mu.m or less, and
particularly preferably be 2 .mu.m or less in terms of the
manufacturing cost since a large energy is required to provide a
thicker layer.
A method of providing a water receptive layer is not particularly
limited, methods that can be used as appropriately include
anodizing method, evaporation method, CVD method, sol-gel method,
sputtering method, ion plating method, diffusion method and the
like. In addition, a method by applying a solution in which hollow
particles mixed in a hydrophilic resin or a sol-gel liquid can be
used.
Among those, it is preferable that a layer of highly hydrophilic
aluminum oxide is formed by anodizing an aluminum plate surface. A
layer obtained is of hydrophilic and has a high hardness, thereby
allowing the surface of a support to increase its abrasion
resistance. Since it has a high-speed treatment suitability, a high
productivity can be obtained.
Anodizing treatment can be performed in the same method as in a
method conventionally performed in this field of technology.
Concretely, if direct current or alternating current is allowed to
flow in an aluminum plate in an aqueous solution or a non-aqueous
solution containing a single or two or more kinds of sulfuric acid
in combination, phosphoric acid, chromic acid, oxalic acid,
sulfamic acid, benzenesulfonic acid or the like, an anodized layer
that is a water receptive layer can be formed on the surface of an
aluminum plate.
In this case, components normally contained in an aluminum plate,
an electrode, city water, an underground water or the like may be
contained in an electrolyte. A second and a third components may be
further added thereto. The second and third components for example
may include metal ions such as Na, K, Mg, Li, Ca, Ti, Al, V, Cr,
Mn, Fe, Co, Ni, Cu and Zn; cation such as ammonium ion; anion such
as nitrate ion, carbonate ion, chloride ion, phosphate ion,
fluoride ion, sulfite ion, titanate ion, silicate ion and borate
ion. Each of them may be contained in the concentration of
approximately 0 to 10,000 ppm in an electrolyte.
Although the conditions of anodizing treatment can not be
indiscriminately determined since they are variously changed
according to an electrolyte to be used, generally appropriate
conditions are the concentration of an electrolyte: 1 to 80 wt %,
the temperature of an electrolyte: 5 to 70.degree. C., the current
density: 0.5 to 60 A/dm.sup.2, the voltage: 1 to 100 V and the time
of electrolysis: 15 seconds to 50 minutes and they are so
controlled as to produce the desired amount of an anodized layer.
In addition, the methods as described in JP 54-81133 A, JP 57-47894
A, JP 57-51289 A, JP 57-51290 A, JP 57-54300 A, JP 57-136596 A, JP
58-107498 A, JP 60-200256 A, JP 62-136596 A, JP 63-176494 A, JP
4-176897 A, JP 4-280997 A, JP 6-207299 A, JP 5-24377 A, JP 5-32083
A, JP 5-125597 A, JP 5-195291 A or the like may be used.
It is preferable that a sulfuric acid solution is used as an
electrolyte as described in JP 54-12853 A and JP 48-45303 A among
others. It is preferable that the concentration of sulfuric acid in
an electrolyte is 10 to 300 g/L (1 to 30 wt %). In addition, the
concentration of aluminum ion should preferably be 1 to 25 g/L (0.1
to 2.5 wt %), and more preferably be 2 to 10 g/L (0.2 to 1 wt %).
An electrolyte like this can be prepared by adding aluminum sulfate
or the like to a diluted sulfuric acid of concentration 50 to 200
g/L, for example.
If anodizing treatment is performed in an electrolyte containing
sulfuric acid, either of direct current or alternating current can
be impressed in-between an aluminum plate and an opposite pole.
If direct current is impressed to an aluminum plate, the current
density should preferably be 1 to 60 A/dm.sup.2, and more
preferably to be 5 to 40 A/dm.sup.2.
If anodizing treatment is continuously performed, it is preferable
that in order to prevent so-called "burning" caused by
concentration of current on a part of an aluminum plate, current
with low current density of 5 to 10 A/dm.sup.2 be allowed to flow
at the beginning of anodizing treatment and the current density be
increased to 30 to 50 A/dm.sup.2 or higher while anodizing
treatment progresses.
It is preferable that if anodizing treatment is continuously
performed, the treatment is performed by an electric power
supplying system via solution, in which electric power is supplied
to an aluminum plate through an electrolyte.
A porous layer having many holes called pore (micropore) is
obtained by performing anodizing treatment under the conditions
like this. Generally, its average pore diameter is about 5 to 50
nm, and its average pore density is about 300 to 800
pcs/.mu.m.sup.2.
Among these anodizing treatments, the method of performing
anodizing treatment at a high current density in a sulfuric acid
electrolyte as described in GB 1,412,768 and the method of
performing anodizing treatment in phosphoric acid as an
electrolytic as described in U.S. Pat. No. 3,511,661 are
preferable. In addition, a multi-stage anodizing treatment in which
anodizing treatment is performed in sulfuric acid and subsequent
anodizing treatment in phosphoric acid and the like may be
performed.
In the present invention, an anodized layer should preferably be of
0.1 g/m.sup.2 or more from the view point of scratch resistance and
press life, more preferably be 0.3 g/m.sup.2 or more, and
particularly preferably 2 g/m.sup.2 or more. In addition, since a
large amount of energy is required to provide a thicker layer, it
should preferably be 100 g/m.sup.2 or less, more preferably be 40
g/m.sup.2 or less, and particularly preferably be 20 g/m.sup.2 or
less.
Generally, a layer of 4 g/m.sup.2 is equivalent to that of about 1
.mu.m thickness.
Device for electrolysis as described in JP 48-26638 A, JP 47-18739
A, JP 58-24517 B or the like may be used for anodizing
treatment.
Among those, device as shown in FIG. 4 is preferably used. FIG. 4
is a schematic view that shows one example of device which performs
anodizing treatment on an aluminum plate surface. In anodizing
device 410, an aluminum plate 416 is transferred as shown by an
arrow in FIG. 4. The aluminum plate 416 is positively charged by a
feeding electrode 420 in a feeding bath 412 where an electrolyte
418 is stored. Then, after the aluminum plate 416 is transferred
upward by a roller 422 in the feeding bath 412 and the direction of
the transfer is changed downward by a nip roller 424, the plate is
transferred to an electrolytic cell 414 where an electrolyte 426 is
stored and the direction of the plate is changed to a horizontal
direction by a roller 428. Thereafter, an anodized layer is formed
on the surface of the aluminum plate 416 by negatively charging the
plate with an electrolytic electrode 430, and the aluminum plate
416 coming out of the electrolytic cell 414 is transferred to a
following process. In the anodizing treatment device 410, direction
changeover means is composed of the roller 422, the nip roller 424,
and the roller 428. The aluminum plate 416 is transferred in a
mountain shape and a reversed U shape between the feeding bath 412
and the electrolytic cell 414 by the rollers 422, 424 and 428. The
feeding electrode 420 and the electrolytic electrode 430 are
connected to a direct current power supply 434.
The anodizing device 410 as shown in FIG. 4 is characterized by the
feeding bath 412 and the electrolytic cell 414 partitioned with a
bath wall 432, and transferring the aluminum plate 416 in a
mountain shape and in a reversed U shape between the baths, thereby
length of the aluminum plate 416 between the baths can be made to
the shortest. Consequently, since the entire length of the
anodizing device 410 can be shortened, the cost of equipment can be
reduced. In addition, since the aluminum plate 416 is transferred
in a mountain shape and a reversed U shape, the necessity of
forming an aperture in the bath walls of each of the baths 412 and
414, through which the aluminum plate 416 is allowed to pass, is
eliminated. Therefore, an amount of a supplied solution required to
keep a solution level at a predetermined level in each bath 412 and
414 can be reduced, so that the operation cost can be reduced.
Micro recesses called micropores are evenly formed on the surface
of the anodized layer. The density of micropores existent in the
anodized layer can be adjusted by selecting the treatment
conditions appropriately. Thermal conductivity in a layer thickness
direction of the anodized layer can be set at 0.05 to 0.5 W/(mK) by
increasing the density of a micropore.
In the third aspect according to the present invention, it is
preferable that after anodizing treatment is performed, pore
widening treatment to widen the pore diameter of the micropore is
performed to lower thermal conductivity. That is, this pore
widening treatment dissolves the anodized layer to expand the pore
diameter by dipping the aluminum plate on which the anodized layer
is formed in an acid aqueous solution or an alkali aqueous
solution. In performing pore widening treatment, a dissolved amount
of the anodized layer should preferably be 0.01 to 20 g/m.sup.2,
more preferably be 0.1 to 5 g/m.sup.2, and particularly preferably
be 0.2 to 4 g/m.sup.2.
When an acid aqueous solution is used for pore widening treatment,
it is preferable that, inorganic acids such as sulfuric acid,
phosphoric acid, nitric acid, hydrochloric acid or an aqueous
solution of mixture of these are used. The concentration of the
acid aqueous solution should preferably be 10 to 1,000 g/L, and
more preferably be 20 to 500 g/L. The temperature of the acid
aqueous solution should preferably be 10 to 90.degree. C., and more
preferably be 30 to 70.degree. C. The time for dipping into the
acid aqueous solution should preferably be 1 to 300 seconds, and
more preferably be 2 to 100 seconds.
On the other hand, if an alkali aqueous solution is used for pore
widening treatment, it is preferable that at least an alkali
aqueous solution selected from a group consisting of sodium
hydroxide, potassium hydroxide and lithium hydroxide is used. The
pH of an alkali aqueous solution is preferably be 10 to 13, and
more preferably be 11.5 to 13.0. The temperature of the alkali
aqueous solution should preferably be 10 to 90.degree. C., and more
preferably be 30 to 50.degree. C. The time for dipping into the
alkali aqueous solution should preferably be 1 to 500 seconds, and
more preferably to 2 to 100 seconds.
In addition to the aforementioned anodized layer, the water
receptive layer may be an inorganic layer provided by sputtering
method, CVD method or the like. The compounds constituting an
inorganic layer may include oxide, nitride, silicate, borate and
carbide. Further, the inorganic layer may be composed of either
only a single compound or a mixture of compounds.
The compounds constituting an inorganic layer may concretely
include aluminum oxide, silicon oxide, titanium oxide, zirconium
oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum
oxide, molybdenum oxide, tungsten oxide, chromium oxide; aluminum
nitride, silicon nitride, titanium nitride, zirconium nitride,
hafnium nitride, vanadium nitride, niobium nitride, tantalum
nitride, molybdenum nitride, tungsten nitride, chromium nitride,
boron nitride; titanium silicide, zirconium silicide, hafnium
silicide, vanadium silicide, niobium silicide, tantalum silicide,
molybdenum silicide, tungsten silicide, chromium silicide; titanium
boride, zirconium boride, hafnium boride, vanadium boride, niobium
boride, tantalum boride, molybdenum boride, tungsten boride,
chromium boride; aluminum carbide, silicon carbide, titanium
carbide, zirconium carbide, hafnium carbide, vanadium carbide,
niobium carbide, tantalum carbide, molybdenum carbide, tungsten
carbide and chromium carbide.
One of the preferred forms of the water receptive layer is either
having the density of 1,000 to 3,200 kg/M.sup.2, or porosity of 20
to 70%.
In addition, in order to form a layer of a low density and
excellent heat insulation on an aluminum plate, treatment with
glasses such as silica, soda glass and borosilicate glass and the
aforementioned anodized layer formation treatment are preferably
used. Among them, anodizing treatment can form a micropore to be a
predetermined porosity by selecting the conditions of anodizing
treatment. This treatment is preferred from the view point that a
desired low-density layer can easily be formed by controlling the
volume of micropores according to the conditions of anodizing
treatment and of subsequent treatments.
As a concrete method of controlling the density of a layer, by
performing anodizing treatment for a long period of time while
keeping the current density low, many fine vacancies are formed and
a good-quality, low-density layer is likely to be formed. In
addition, it is known that if the temperature or the concentration
of an electrolyte is increased, the diameter of the hole formed on
the surface of the anodized layer is likely to be increased. A
layer with a desired density may be formed by combining the
aforementioned method with sealing treatment to be described later.
In addition, a method of dissolving micropores with an acid
solution or an alkali solution after anodizing treatment may be
used so as to make the once formed anodized layer in be a
low-density layer. Moreover, these controlling methods may be
appropriately selected by those skilled in the art.
A low-density layer is formed under the aforementioned conditions.
The density of the formed layer can be found by, for example, the
following equation from the weight measurement by Mason method (a
method of measuring weight of an anodized layer by dissolving the
layer in a mixture of chromic acid and phosphoric acid) and the
thickness of the layer found by observing the cross section of the
layer with SEM: Density (kg/m.sup.3)=(weight of layer per unit
area/thickness of layer)
If the density of the formed layer is less than 1,000 kg/m.sup.3,
the strength of the layer may become weak, thereby badly affecting
image forming characteristics and press life, and if the density
exceeds 3,200 kg/m.sup.3, sufficient heat insulation can not be
obtained, thereby decreasing a sensitivity-improving effect.
Porosity of a water receptive layer should preferably be 20 to 70%,
more preferably be 30 to 60%, and particularly preferably be 40 to
50%. If the porosity of a water receptive layer is 20% or more,
thermal diffusion into a support is sufficiently suppressed and a
sensitivity-improving effect can be sufficiently obtained. If the
porosity of a water receptive layer is 70% or less, a problem that
dirt is generated in non-image areas does not easily take
place.
The porosity of a water receptive layer here means a volume ratio
of an area of holes in the layer. In the case of an anodized layer,
the porosity can be found from a pore diameter, depth, and number
of pores obtained by SEM observation.
After a layer with a density 1,000 to 3,200 kg/m.sup.3 is produced,
sealing treatment to be described later is performed to increase
the surface area of a support one to thirty times of the apparent
surface area. The apparent surface area here is, for example, an
area of 10,000 mm.sup.2 if graining treatment and anodizing
treatment are performed on only one side of a printing plate of 100
mm.times.100 mm, and an area of 20,000 mm.sup.2 if graining
treatment and anodizing treatment are performed on both sides of
the printing plate, the both sides being used as the printing
plate.
<Sealing Treatment>
In the present invention, sealing treatment for sealing micropores
existent in the anodized layer may be performed as required.
Sealing treatment may be performed according to the publicly known
methods such as boiling water treatment, hot water treatment,
steaming treatment, sodium silicate treatment, nitrite treatment
and ammonium acetate treatment. The sealing treatment may be
performed with the device and by the methods as described in JP
56-12518 B, JP 4-4194 A, JP 5-202496 A, JP 5-179482 A or the like,
for example.
<Treatment for Water Wettability>
Treatment for water wettability may be performed after anodizing
treatment or sealing treatment is performed. Treatments for water
wettability include potassium fluorozirconate treatment as
described in U.S. Pat. No. 2,946,636, phosphomolybdate treatment as
described in U.S. Pat. No. 3,201,247, alkyltitanate treatment as
described in GB 1,108,559, polyacrylic acid treatment as described
in DE 1,091,433, polyvinylphosphonic acid treatment as described in
DE 1,134,093 and GB 1,230,447, phosphonic acid treatment as
described in JP 44-6409 B, phytic acid treatment as described in
U.S. Pat. No. 3,307,951, treatment with a salt of lipophilic
organic high-molecular compound and divalent metal as described in
JP 58-16893 A and JP 58-18291 A, treatment providing undercoat
layer of hydrophilic cellulose (for example,
carboxylmethylcellulose) containing water-soluble metallic salts
(for example, zinc acetate) as described in U.S. Pat. No. 3,860,426
and treatment to apply undercoating of water-soluble polymer having
sulfo group as described in JP 59-101651 A.
In addition, compounds used for undercoating treatment include
phosphate as described in JP 62-019494 A, water-soluble epoxide
compound as described in JP 62-033692 A, phosphoric acid-treated
starch as described in JP 62-097892 A, diamines as described in JP
63-056498 A, inorganic amino acid or organic amino acid as
described in JP 63-130391 A, organic phosphonic acid containing
carboxy group or hydroxy group as described in JP 63-145092 A,
compounds containing amino group and phosphonic group as described
in JP 63-165183 A, specified carboxylic acid derivatives as
described in JP 2-316290 A, phosphoric ester as described in JP
3-215095 A, compounds having one amino group and one oxoacid group
of phosphor as described in JP 3-261592 A, aliphatic or aromatic
sulfonic acid such as phenylsulfonic acid as described in JP
5-246171 A, compounds containing S atom such like thiosalicylic
acid as described in JP 1-301745 A, and compounds having oxoacid
group of phosphor or the like as described in JP 4-282637 A.
In addition, coloring by an acid dye as described in JP 60-64352 A
can be performed.
It is preferable that treatment for water wettability is performed
by a method of dipping an object into an aqueous solution
containing alkali metal silicates such as sodium silicate and
potassium silicate, a method of forming a hydrophilic undercoat
layer by applying a hydrophilic vinylpolmer or a hydrophilic
compound or the like.
Treatment for water wettability with an aqueous solution containing
alkali metal silicates such as sodium silicate and potassium
silicate can be performed in accordance with the methods and steps
as described in U.S. Pat. Nos. 2,714,066 and 3,181,461.
Alkali metal silicates include sodium silicate, potassium silicate
and lithium silicate. An aqueous solution containing alkali metal
silicates may contain an appropriate amount of sodium hydroxide,
potassium hydroxide, lithium hydroxide or the like.
In addition, an aqueous solution containing alkali metal silicates
may contain alkaline-earth metallic salts or fourth group (IVA
group) metallic salts. Examples of alkaline-earth metallic salts
are nitrates such as calcium nitrate, strontium nitrate, magnesium
nitrate and barium nitrate; sulfates; chlorides; phosphates;
acetates; oxalates; and borates. Examples of fourth group (IVA
group) metallic salts are titanium tetrachloride, titanium
trichloride, potassium titanium fluoride, potassium titanium
oxalate, titanium sulfate, titanium tetraiodide, zirconium oxide
chloride, zirconium dioxide, zirconium oxychloride, zirconium
tetrachloride. These alkali earth metallic salts and fourth group
(IVA group) metallic salts can be used in either of a single form
or combinations of two kinds or more.
An amount of Si adsorbed by alkali metal silicate treatment can be
measured with a flourescent X-ray analyzer, and its adsorbed amount
should preferably be 1.0 to 15.0 mg/m.sup.2.
An effect to improve insolubility of the surface of a support for a
lithographic printing plate with respect to an alkali developer can
be obtained by performing this alkali metal silicate treatment.
Further, since the elution of an aluminum component into the
developer is suppressed, the generation of a development scum
attributable to the exhaust of the developer can be reduced.
Since a support for a lithographic printing plate according to the
present invention is excellent in contact characteristics between
the image recording layer and the support as aforementioned, a
sufficient press life can be obtained even when alkali metal
silicate treatment is performed. Consequently, even when alkali
metal silicate treatment is performed, only the advantages that
scum resistance is improved and the generation of a development
scum can be reduced can be enjoyed, with no anxiety about
deterioration of press life.
In addition, treatment for water wettability by forming a
hydrophilic undercoat layer may be performed under the conditions
and steps as described in JP 59-101651 A and JP 60-149491 A.
An example of hydrophilic vinylpolymer to be used in this method is
a copolymer of vinylpolymerizable compound having sulfo group such
as polyvinylsulfonic acid and p-styrenesulfonic acid that has sulfo
group, with ordinary vinylpolymerizable compound such as
(meta)acrylic alkylester. In addition, an example of a hydrophilic
compound to be used in the method is a compound containing at least
one selected from a group consisting of --NH.sub.2 group, --COOH
group, and sulfo group.
<Water Washing Treatment>
It is preferable that water washing is performed after
aforementioned each treatment is finished. Pure water, well water,
city water or the like can be used for water washing. It is
acceptable that a nip device may be used to prevent the treatment
solution from being brought into the next process.
<Aluminum Plate (Rolled Aluminum)>
An aluminum plate publicly known can be used to obtain a support
for a lithographic printing plate according to the present
invention. An aluminum plate used in the present invention is a
metal having an aluminum which is stable in dimension as a main
component, and is composed of aluminum or aluminum alloy. Besides a
pure aluminum plate, an alloy plate containing aluminum as main
component and a trace of different elements can be used.
In the present invention, various substrates composed of the
aforementioned aluminum or aluminum alloys, and referred to
collectively as an aluminum plate. Different elements that may be
contained in the aluminum alloy are silicon, iron, manganese,
copper, magnesium, chromium, zinc, bismuth, nickel, titanium or the
like, and the contents of the different elements in the alloy is 10
wt % or less.
Like this, the composition of an aluminum plate used in the present
invention is not specified. For example, the materials
conventionally known as described in Aluminum Handbook 4th edition
(published by Japan Light Metal Association in 1990) that are, for
example, an Al--Mn system aluminum plate of JIS A1050, JIS A1100,
JIS A1070, JIS A3004 containing Mn, the internationally registered
alloy 3103A and the like can be appropriately utilized. In
addition, an Al--Mg system alloy and Al--Mn--Mg system alloy (JIS
A3005) into which 0.1 wt % or more of Mg is added can be used to
increase tensile strength. Moreover, Al--Zr system or Al--Si system
alloy containing Zr or Si can be used. Further, Al--Mg--Si system
alloy can also be used.
With regard to JIS1050 materials, the arts that have been proposed
by the inventors of the present invention are described in JP
59-153861 A, JP 61-51395 A, JP 62-146694 A, JP 60-215725 A, JP
60-215726 A, JP 60-215727 A, JP 60-216728 A, JP 61-272367 A, JP
58-11759 A, JP 58-42493 A, JP 58-221254 A, JP 62-148295 A, JP
4-254545 A, JP 4-165041 A, JP 3-68939 B, JP 3-234594 A, JP 1-47545
B and JP 62-140894 A. Also known are the arts which have been
described in JP 1-35910 B and JP 55-28874 B.
With regard to JIS1070 materials, the arts which have been proposed
by the inventors of the present invention are described in JP
7-81264 A, JP 7-305133 A, JP 8-49034 A, JP 8-73974 A, JP 8-108659 A
and JP 8-92679 A.
With regard to Al--Mg system alloys, the arts which have been
proposed by the inventors of the present invention are described in
JP 62-5080 B, JP 63-60823 B, JP 3-61753 B, JP 60-203496 A, JP
60-203497 A, JP 3-11635 B, JP 61-274993 A, JP 62-23794 A, JP
63-47347 A, JP 63-47348 A, JP 63-47349 A, JP 64-1293 A, JP
63-135294 A, JP 63-87288 A, JP 4-73392 B, JP 7-100844 B, JP
62-149856 A, JP 4-73394 B, JP 62-181191 A, JP 5-76530 B, JP
63-30294 A and JP 6-37116 B. The arts are also described in JP
2-215599 A and JP 61-201747 A.
With regard to Al--Mn system alloys, the arts which have been
proposed by the inventors of the present invention are described in
JP 60-230951 A, JP 1-306288 A and JP 2-293189 A. In addition,
others are also described in JP 54-42284 B, JP 4-19290 B, JP
4-19291 B, JP 4-19292 B, JP 61-35995 A, JP 64-51992 A, JP 4-226394
A, U.S. Pat. Nos. 5,009,722, 5,028,276 or the like.
With regard to Al--Mn--Mg system alloys, the arts which have been
proposed by the inventors of the present invention are described in
JP 62-86143 A and JP 3-222796 A. In addition, others are also
described in JP 63-60824 B, JP 60-63346 A, JP 60-63347 A, JP
1-293350 A, EP 223,737, U.S. Pat. No. 4,818,300,. GB 1,222,777 or
the like.
With regard to Al--Zr system alloys, the arts which have been
proposed by the inventors of the present invention are described in
JP 63-15978 B and JP 61-51395 A. In addition, others are also
described in JP 63-143234 A, JP 63-143235 A, or the like.
With regard to Al--Mg--Si system alloys, the arts are described in
GB 1,421,710.
The following method can be, for example, employed to prepare a
plate from an aluminum alloy. First, purification treatment is
performed on a molten aluminum alloy adjusted to a predetermined
alloy component content and is cast according to a normal method.
For the purification treatment, in order to remove unnecessary
gases such as hydrogen from the molten metal, such treatment is
performed as flux treatment; degassing treatment with argon gas,
chlorine gas or the like; filtering treatment using a so-called
rigid media filter such as ceramics tube filter, ceramics form
filter or the like, a filter using alumina flake, alumina ball and
the like as filtering media, or a glass cloth filter, or the like;
or a combination of degassing treatment with filtering
treatment.
It is preferable that purification treatment as aforementioned be
performed to prevent defects caused by foreign matter such as
non-metal inclusion in the molten metal and oxides, and defects
caused by gasses dissolved in the molten metal. Filtering of a
molten metal is described in JP 6-57432 A, JP 3-162530 A, JP
5-140659 A, JP 4-231425 A, JP 4-276031 A, JP 5-311261 A, JP
6-136466 A or the like. In addition, degassing of a molten metal is
described in JP 5-51659 A, JP 5-49148 A or the like. The inventors
of the present invention have also proposed an art regarding
degassing of a molten metal in JP 7-40017 A.
Next, the molten metal to which purification treatment is performed
as aforementioned is cast. Casting uses either a method by using a
solid mold represented by DC casting method and a method by using a
drive mold represented by continuous casting method.
In DC casting, a molten metal is solidified at a cooling rate
within a range of 0.5 to 30.degree. C./sec. If the cooling rate is
less than 0.5.degree. C./sec, many large intermetallic compounds
may be formed. When DC casting is performed, an ingot plate 300 to
800 mm in thickness can be produced. Chipping is performed on this
ingot according to a usual method as required, and normally, it is
cut by 1 to 30 mm of the surface layer, and by 1 to 10 mm
preferably. Before and after the chipping, soaking treatment is
performed as required. If heat soaking treatment is performed, heat
treatment is performed at 450 to 620.degree. C. for 1 to 48 hours
so as not to allow intermetallic compounds to become larger. If
treatment time is shorter than 1 hour, an effect of soaking
treatment may be insufficient.
Thereafter, hot rolling and cold rolling are performed to produce
the rolled plate of an aluminum plate. It is appropriate that the
starting temperature of hot rolling is 350 to 500.degree. C. Before
and after or halfway of hot rolling, intermediate annealing may be
performed. The conditions of intermediate annealing are either a
heating with a batch type annealer at 280 to 600.degree. C. for 2
to 20 hours, more preferably at 350 to 500.degree. C. for 2 to 10
hours, or a heating with continuous type annealer at 400 to
600.degree. C. for 6 minutes or less, and more preferably at 450 to
550.degree. C. for 2 minutes or less. Crystal structure can be
fined by heating an aluminum plate with a continuous type annealer
at a temperature rising speed of 10 to 200.degree. C./sec.
With regard to an aluminum plate finished to a plate of a
predetermined thickness, for example, 0.1 to 0.5 mm by the
aforementioned processes, in addition, the flatness thereof may be
improved with correcting device such as a roller leveler and a
tension leveler. Although improvement of the flatness may be
performed after the aluminum plate is cut into a sheet form, it is
preferable that the improvement is performed in a continuous coil
form to enhance its productivity. In addition, an aluminum plate is
allowed to pass through a slitter line in order to process the
aluminum plate to have a predetermined plate width further, an oil
film may be provided on the surface of the aluminum plate to
prevent generation of scratches due to friction between the
aluminum plates. An oil film which is volatile or non-volatile is
appropriately used as required.
On the other hand, methods to be industrially used as continuous
casting method include two-roll method (Hunter method), method with
cold rolling represented by 3C method, two-belt method (Hazellet
method), a method using a cooling belt and a cooling block
represented by Alysuisse caster II model. If continuous casting
method is used, solidification develops at a cooling rate in a
range of 100 to 1,000.degree. C./sec. Continuous casting method is
characterized by that the solid solubility percentage of an alloy
component with respect to an aluminum matrix can be increased since
it generally has a faster cooling speed than that of DC casting
method. With regard to continuous casting method, the arts which
have been proposed by the inventors of the present invention are
described in JP 3-79798 A, JP 5-201166 A, JP 5-156414 A, JP
6-262203 A, JP 6-122949 A, JP 6-210406 A, JP 6-26308 A and the
like.
If continuous casting method is performed, for example, with a
method using a chill roll such as Hunter method or the like, since
a cast plate of thickness 1 to 10 mm can be directly and
continuously produced, resulting in a merit that hot rolling
process can be omitted. In addition, if a method with a cooling
belt such as Hazellet method or the like is used, a cast plate of
thickness 10 to 50 mm can be produced. Generally, a continuously
cast rolled-plate of thickness 1 to 10 mm can be obtained by
disposing a hot roll just after casting to continuously roll a
plate.
These continuously cast rolled plates are subjected to treatments
such as cold rolling, intermediate annealing, improvement of
flatness, treatment of slit and the like, and are finally finished
into a predetermined thickness, for example, 0.1 to 0.5 mm. With
regard to intermediate annealing and cold rolling conditions in
case where continuous casting method is used, the arts which have
been proposed by the inventors of the present invention are
described in JP 6-220593 A, JP 6-210308 A, JP 7-54111 A, JP 8-92709
A and the like.
An aluminum plate thus manufactured is expected to have various
characteristics as mentioned below.
It is preferable, regarding strength of an aluminum plate, 0.2%
proof stress is 140 MPa or more to obtain an elasticity required as
a support for a lithographic printing plate. In addition, it is
preferable that 0.2% proof stress after heating treatment is
performed at 270.degree. C. for 3 to 10 minutes is 80 MPa or more,
more preferably 100 Mpa or more in order to obtain an elasticity to
some extent even if burning treatment is performed. Particularly,
if an aluminum plate requires some elasticity, an aluminum material
to which Mg or Mn is added can be adopted. Attachment of a plate to
the plate cylinder of a printing machine, however, deteriorates if
the elasticity is enhanced. For that reason, the material and an
amount of the trace components to be added are appropriately
selected in accordance with the application. In connection with
this, the arts which have been proposed by the inventors of the
present invention are described in JP 7-126820 A, JP 62-140894 A
and the like.
Since the crystal texture of an aluminum plate surface may cause a
defect in surface quality if chemical graining treatment or
electrochemical graining treatment is performed on an aluminum
plate, it is preferable that the crystal texture graining on the
surface is not too coarse. The width of a particle of the crystal
texture on the surface of an aluminum plate should preferably be
200 .mu.m or less, more preferably be 100 .mu.m or less, and
further preferably be 50 .mu.m or less. In addition, the length of
a particle of the crystal texture should preferably be 5,000 .mu.m
or less, more preferably be 1,000 .mu.m or less, and further
preferably be 500 .mu.m or less. In connection with these, the arts
which have been proposed by the inventors of the present invention
are described in JP 6-218495 A, JP 7-39906 A, JP 7-124609 A and the
like.
Since a defect in surface quality may take place due to the uneven
distribution of an alloy component on the surface of an aluminum
plate if chemical graining treatment or electrochemical graining
treatment is performed, it is preferable that the distribution of
the alloy component is not too uneven on the surface. With regard
to these, the arts which have been proposed by the inventors of the
present invention are described in JP 6-48058 A, JP 5-301478 A, JP
7-132689 A and the like.
The size or density of intermetallic compounds in an aluminum plate
may affect chemical graining treatment or electrochemical graining
treatment In connection with this, the arts which have been
proposed by the inventors of the present invention are described in
JP 7-138687 A, JP 4-254545 A and the like.
According to the present invention, for use, the aluminum plate as
described above can be provided with asperities by laminating
rolling, transfer or the like in the final rolling process.
An aluminum plate used in the present invention is a continuous
belt-like sheet material or plate material. That is, an aluminum
web is acceptable and a sheet material cut into a size or the like
corresponding to a presensitized plate to be shipped as a product
is also acceptable.
Since a scratch on the surface of an aluminum plate may become a
defect when processed into a support for a lithographic printing
plate, it is necessary to suppress as much as possible the
generation of a scratch at a stage before a surface treatment
process to produce a support for a lithographic printing plate is
performed For that reason, it is preferable that an aluminum plate
is packed in a stable form and style so as to avoid being
scratched.
In case of aluminum web, as a style of packing aluminum, for
example, a hard board and a felt sheet are laid over a pallet made
of iron, toroidal cardboards are put at both ends of a product, the
entire product is wrapped with a polymer tube, a wooden toroid is
inserted into the inner diameter section of a coil, the periphery
of a coil is covered with a felt sheet, the product is fastened
with a hoop iron and the indication is attached to its periphery.
In addition, a polyethylene film can be used for packing material,
and a needle felt and a hard board can be used for buffer. There
are various packing forms besides this one. As long as it provides
stable and scratch-free transportation or the like, packing is not
limited to this method mentioned above.
The thickness of an aluminum plate used in the present invention is
about 0.1 to 0.6 mm, preferably be 0.15 to 0.4 mm, and more
preferably be 0.2 to 0.3 mm. This thickness can be appropriately
changed according to the size of a printing machine, the size of a
printing plate, the request of a user, or the like.
[Presensitized Plate]
A presensitized plate according to the present invention can be
prepared by providing an image recording layer such as a
photosensitive layer, thermosensitive layer or the like as
illustrated below on the support for a lithographic printing plate.
An image recording layer is not particularly limited, and preferred
examples include conventional positive type, conventional negative
type, photopolymer type, thermal positive type, thermal negative
type and development-dispensable type that can be developed on a
printer. Moreover, in the case of a support for a lithographic
printing plate of the third aspect according to the present
invention, a type using heat to form an image is preferable, for
example, preferably taken up are thermal positive type, thermal
negative type and development-dispensable type.
Detailedly described below are these preferred image recording
layers.
<Conventional Positive Type>
As a photosensitive resin composition used suitably for the
photosensitive layer of the conventional positive type, for
example, a composition containing an o-quinonediazide compound and
a high-molecular compound that is water-insoluble and
alkali-soluble (hereinafter, referred to as an "alkali-soluble
high-molecular compound") is cited.
Cited as such an o-quinonediazide compound are, for example, the
ester of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride and
phenol-formaldehyde resin or cresol-formaldehyde resin, and the
ester of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride and
pyrogallol-acetone resin, which is described in U.S. Pat. No.
3,635,709.
Cited as such an alkali-soluble high-molecular compound are, for
example, phenol-formaldehyde resin, cresol-formaldehyde resin,
phenol-cresol-formaldehyde co-condensed resin, polyhydroxystyrene,
copolymer of N-(4-hydroxyphenyl)methacrylamide, carboxy
group-containing polymer described in JP 7-36184 A, acrylic resin
containing a phenolic hydroxy group as described in JP 51-34711 A,
acrylic resin containing a sulfonamide group described in JP 2-866
A, and urethane resin.
Furthermore, it is preferable that a compound such as a sensitivity
regulator, a printing agent and a dye, which are described in
[0024] to [0027] of JP 7-92660 A, or a surfactant for improving a
coating property of the photosensitive resin composition, which is
as described in [0031] of JP 7-92660 A, is added to the
photosensitive resin composition.
<Conventional Negative Type>
As a photosensitive resin composition used suitably for the
photosensitive layer of the conventional negative type, a
composition containing diazo resin and a high-molecular compound
that is alkali-soluble or alkali-swellable (hereinafter, referred
to as a "binding agent") is cited.
Cited as such diazo resin is, for example, a condensate of an
aromatic diazonium salt and a compound containing an active
carbonyl group such as formaldehyde, and an inorganic salt of
organic solvent-soluble diazo resin, which is a reaction product of
a condensate of p-diazo phenyl amines group and formaldehyde with
hexafluorophosphate or tetrafluoroborate. Particularly, a
high-molecular-weight diazo compound containing 20 mol % or more of
a hexamer or larger, which is described in JP 59-78340 A, is
preferable.
For example, copolymer containing, as an essential component,
acrylic acid, methacrylic acid, crotonic acid or maleic acid is
cited as a suitable binding agent. Specifically, multi-copolymer of
monomer such as 2-hydroxyethyl(meth)acrylate, (meth)acrylonitrile
and (meth)acrylic acid, which is as described in JP 50-118802 A,
and multi-copolymer composed of alkylacrylate, (metha)acrylonitrile
and unsaturated carboxylic acid, which is as described in JP
56-4144 A, are cited.
Furthermore, to the photosensitive resin composition, it is
preferable to add a compound such as a printing agent, a dye, a
plasticizer for imparting the flexibility of the coating layer,
abrasion resistance, a development accelerator, and a surfactant
for improving the coating property, which are described in [0014]
and [0015] of JP 7-281425 A.
It is preferable that an intermediate layer containing a
high-molecular compound having a constituent with an acid group and
a constituent with an onium group, which is described in JP
2000-105462 A, is provided as an undercoat layer of the
above-described positive or negative photosensitive layer of the
conventional type.
<Photopolymer Type>
A photosensitive composition of a photopolymerization type
(hereinafter, referred to as a "photopolymerizable composition"),
which is used suitably for the photosensitive layer of the
photopolymer type, contains a compound containing ethylenic
unsaturated bonding capable of addition polymerization
(hereinafter, simply referred to as a "compound containing
ethylenic unsaturated bonding"), a photopolymerization initiator
and a high-molecular binding agent as essential components.
According to needs, the photopolymerizable composition contains
various compounds such as a colorant, a plasticizer and a thermal
polymerization inhibitor.
A compound containing ethylenic unsaturated bonding, which is
contained in the photopolymerizable composition, is a compound
having the ethylenic unsaturated bonding as carrying out addition
polymerization, crosslinking and curing by the action of the
photopolymerization initiator when the photopolymerizable
composition is irradiated by active light ray. The compound
containing the ethylenic unsaturated bonding can be arbitrarily
selected from compounds, each having at least one, and preferably
two or more of end ethylenic unsaturated bondings. For example,
this compound has a chemical form of monomer, prepolymer (that is,
dimmer, trimer or oligomer), a mixture thereof, a copolymer thereof
or the like. Cited as examples of the monomer are the ester of
unsaturated carboxylic acid (for example, acrylic acid, methacrylic
acid, itaconic acid, crotonic acid, isocrotonic acid and maleic
acid) and an aliphatic polyhydric alcohol compound and the amide of
unsaturated carboxylic acid and an aliphatic polyamine compound.
Moreover, a urethane addition polymerizable compound is also
suitable.
As the photopolymerization initiator contained in the
photopolymerizable composition, a variety of photopolymerization
initiators or combined systems of two or more photopolymerization
initiators (photo initiation systems) can be appropriately selected
for use according to a wavelength of a light source to be used. For
example, initiation systems described in [0021] to [0023] of JP
2001-22079 A are preferable.
Since the high-molecular binding agent contained in the
photopolymerizable composition needs not only to function as a
coating layer forming agent for the photopolymerizable composition
but also to dissolve the photosensitive layer in an alkali
developer, an organic high-molecular polymer that is soluble or
swellable in an aqueous solution of alkali is used. As the
above-described high-molecular binding agent, the agent described
in [0036] to [00631 of JP 2001-22079 A.
It is preferable to add the additive described in [0079] to (0088]
of JP 2001-22079 A (for example, a surfactant for improving the
coating property) to the photopolymerizable composition.
Moreover, it is also preferable to provide an oxygen-shieldable
protective layer on the above-described photosensitive layer for
preventing the polymerization inhibiting action of oxygen.
Poly(vinyl alcohol) and a copolymer thereof are cited as a polymer
contained in the oxygen-shieldable protective layer.
Furthermore, it is also preferable that, as a lower layer of the
above-described photosensitive layer, an adhesive layer as
described in [0131] to [0165] of JP 2001-228608 A is provided.
<Thermal Positive Type>
The thermosensitive layer of the thermal positive type contains
alkali-soluble high-molecular compound and a photothermal
conversion agent.
The alkali-soluble high-molecular compound includes a homopolymer
containing an acid group in the polymer, a copolymer thereof and a
mixture thereof. Particularly, the one having an acid group such as
a (1) phenolic hydroxy group (--Ar--OH) and a (2) sulfonamide group
(--SO.sub.2NH--R) is preferable in terms of solubility to the
alkali developer. Above all, the one having the phenolic hydroxy
group is preferable since it is excellent in image-forming
capability in the exposure by an infrared ray laser or the like.
For example, novolac resin such as phenol-formaldehyde resin,
m-cresol-formaldehyde resin, p-cresol-formaldehyde resin,
m-/p-mixed cresol-formaldehyde resin and phenol/cresol (any of m-,
p- and m-/p-mixed may be allowed)-mixed-formaldehyde resin, and
pyrogallol-acetone resin are preferably cited. More specifically,
the polymers described in [0023] to [0042] of JP 2001-305722 A are
preferably used.
The photothermal conversion agent converts exposure energy into
heat to enable efficient release execution of an interaction in an
exposed region of the thermosensitive layer. From a viewpoint of a
recording sensitivity, pigment or dye, which has a light absorbing
band in the infrared band ranging from 700 to 1200 nm in
wavelength, is preferable. Concretely cited as the dye are azo dye,
azo dye in the form of metallic complex salt, pyrazolone azo dye,
naphthoquinone dye, anthraquinone dye, phthalocyanine dye,
carbonium dye, quinonimine dye, methine dye, cyanine dye,
squarylium dyestuff, pyrylium salt, metal thiolate complex (for
example, nickel thiolate complex) and the like. Particularly, the
cyanine dye is preferable and, for example, the cyanine dye
represented by the general formula (I) in JP 2001-305722 A is
cited.
To the composition for use in the thermosensitive layer of the
thermal positive type, it is preferable to add a compound such as a
sensitivity regulator, a printing agent and a dye, and the
surfactant for improving the coating capability, which are similar
to those described in the paragraph of the foregoing conventional
positive type. Specifically, the compounds described in [0053] to
[0059] of JP 2001-305722 A are preferable.
The thermosensitive layer of the thermal positive type may be a
single layer or may have a two-layer structure as described in JP
11-218914 A.
It is preferable to provide an undercoat layer between the
thermosensitive layer of the thermal positive type and a support
thereof. As a component contained in the undercoat layer, the
variety of organic compounds described in [0068] of JP 2001-305722
A are cited.
<Thermal Negative Type>
The thermosensitive layer of the thermal negative type is a
negative thermosensitive layer in which an infrared
laser-irradiated areas are cured to form image areas.
As one of such thermosensitive layers of the thermal negative type,
a polymerizable-type layer (polymerizable layer) is suitably cited.
The polymerizable layer contains an (A) infrared absorbent, a (B)
radical generator (radical polymerization initiator), a (C) radical
polymerizable compound causing a polymerization reaction by the
generated radicals and curing, and a (D) binder polymer.
In the polymerizable layer, the infrared ray absorbed by the
infrared absorbent is converted into heat, then the radical
polymerization initiator such as onium salt is decomposed by the
heat generated, and thus radicals are generated. The radical
polymerizable compound is selected from compounds having end
ethylenic unsaturated bondings, and a chain polymerization reaction
occurs by the generated radicals, and thus the radical
polymerizable compound cures.
As the (A) infrared absorbent, for example, the photothermal
conversion agent contained in the above-described thermosensitive
layer of the thermal positive type is cited. Particularly, the ones
described in [0017] to [0019] of JP 2001-133969 A are cited as
concrete examples of the cyanine dyestuff. The onium salt is cited
as the (B) radical generator. The ones described in [0030] to
[0033] of JP 2001-133969 A are cited as concrete examples of the
onium salt used suitably. The (C) radical polymerizable compound is
selected from compounds, each having at least one, and preferably
two or more of the end ethylenic unsaturated bondings. It is
preferable to use linear organic polymer as the (D) binder polymer,
and linear organic polymer that is soluble or swellable in water or
alkalescent water is selected. Among such polymers, particularly,
(meth)acrylic resin having a benzyl group or an allyl group and a
carboxy group in side chains is excellent in a balance of layer
strength, sensitivity and development property, and is suitable.
For the (C) radical polymerizable compound and the (D) binder
polymer, the ones described in detail in [0036] to [0060] of JP
2001-133969 A can be used. It is also preferable to add the
additives described in [0061] to [0068] of JP 2001-133969 A (for
example, the surfactant for improving the coating property) as
other additives.
Besides the polymerizable-type layer, an acid cross-linkable-type
layer (acid cross-linkable layer) is suitably cited as one of the
thermosensitive layers of the thermal negative type. The acid
cross-linkable layer contains a (E) compound generating acid by
light or heat (hereinafter, referred to as an "acid generator"), a
(F) compound cross-linking by the generated acid (hereinafter,
referred to as a "cross-linking"), and a (G) alkali-soluble
high-molecular compound capable which can react with the
cross-linking agent under the presence of the acid. The (A)
infrared absorbent may be mixed in the acid cross-linkable in order
to absorb the energy of the infrared laser efficiently. Cited as
the (E) acid generator is a compound capable of generating acid by
thermal decomposition, such as a photoinitiator for the
photopolymerization, a color-turning agent (i.e., dye stuff) and an
acid generator for use in microresist or the like. Cited as the (F)
cross-linking agent are an (i) aromatic compound substituted with a
hydroxymethyl group or an alkoxymethyl group, a (ii) compound
having a N-hydroxymethyl group, a N-alkoxymethyl group or a
N-acyloxymethyl group, and an (iii) epoxy compound. As the (G)
alkali-soluble high-molecular compound, novolac resin, polymer
having a hydroxyaryl group in the side chain, and the like are
cited.
<Development-dispensable Type>
There are various types including a thermoplastic particle polymer
type, a microcapsule type, a type containing sulfonic
acid-generating polymer and the like in the thermosensitive layer
of the development-dispensable type. The present invention is
particularly preferable for the development-dispensable type which
can be developed on a printing machine.
In the thermoplastic particle polymer type, (H) hydrophobic
thermowelding resin particles are dispersed in a (J) hydrophilic
polymer matrix, and can be welded by heat of exposed areas and
fused mutually, thus forming hydrophobic areas, that is, image
areas formed by polymers.
The (H) hydrophobic thermowelding resin particles (hereinafter,
referred to as "particulate polymers"), which mutually fuse and
coalesce by the heat, are preferable. The particulate polymers,
which have hydrophilic surfaces and can be dispersed in a
hydrophilic component such as a fountain solution, are preferable.
Suitably cited as the particulate polymers are thermoplastic
particulate polymers described in Research Disclosure No. 33303
(Published in January, 1992), JP 9-123387 A, JP 9-131850 A, JP
9-171249 A, JP 9-171250 A, EP 931,647 A and the like Cited as
concrete examples are homopolymers of monomers of ethylene,
styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl
methacrylate, ethyl methacrylate, vinylidene chloride,
acrylonitrile, vinyl carbazole or the like; copolymers thereof; or
mixtures thereof. Among them, it is preferable to use polystyrene
and poly(methyl methacrylate). The particulate polymers having the
hydrophilic surfaces include: polymers which are hydrophilic
themselves such as polymers constituting the particles, which are
hydrophilic themselves, and polymers to which hydrophilicity is
imparted by introducing hydrophilic groups into main chains or side
chains of the polymers; and polymers of which surfaces are made
hydrophilic by adsorbing hydrophilic polymer such as poly(vinyl
alcohol) and poly(ethylene glycol), hydrophilic oligomer or a
hydrophilic low-molecular weight compound to the surfaces of the
particulate polymers. As the particulate polymers, particulate
polymers having thermoreactive functional groups are more
preferable. The particulate polymers as described above are
dispersed in the (J) hydrophilic high-molecular matrix, and thus
obtaining good on-machine development property in the case of
carrying out development on a machine, and further, the coating
layer strength of the thermosensitive layer is also improved.
As the microcapsule type, a type described in JP 2000-118160 A and
a microcapsule type containing a compound having a thermoreactive
functional group as described in JP 2001-277740 A are preferably
cited.
As the sulfonic acid-generating polymer for use in the type
containing the sulfonic acid-generating polymer, for example,
polymer having a sulfonic acid ester group, a disulfonic group or a
sec- or tert-sulfonamide group in the side chain described in JP
10-282672 A is cited.
The hydrophilic resin can be contained in the thermosensitive layer
of the development-dispensable type, and thus, not only the
on-machine development property would be improved, but also the
coating layer strength of the thermosensitive layer itself would be
improved. Moreover, the hydrophilic resin is cross-linked and
cured, thus making it possible to obtain a presensitized plate
eliminating a necessity of development process. Preferable as the
hydrophilic resin, for example, the one having a hydrophilic group
such as a hydroxy group, a carboxy group, a hydroxyethyl group, a
hydroxypropyl group, an amino group, an aminoethyl group, an
aminopropyl group and a carboxymethyl group, and sol-gel conversion
type bonding resin that is hydrophilic are preferable.
As concrete examples of the hydrophilic resin, the ones enumerated
as the hydrophilic resins for use as the above-described (J)
hydrophilic high-molecular matrix are cited.
Among them, the sol-gel conversion type bonding resin is
preferable.
It is necessary to add the photothermal conversion agent to the
thermosensitive layer of the development-dispensable type. It is
satisfactory that the photothermal conversion agent may be a
substance absorbing light with a wavelength of 700 nm or more, and
a dye similar to the dye for use in the above-described thermal
positive type is particularly preferable.
<Backcoat Layer>
On the reverse side of the presensitized plate of the present
invention, which is obtained by providing various types of image
recording layers on the support for the lithographic printing plate
of the present invention, a backcoat layer composed of an organic
high-molecular compound can be provided according to needs in order
to prevent the image recording layers from being scratched in the
case of stacking the presensitized plate or the like.
<Method of Producing a Presensitized Plate>
Usually, the respective layers of the image recording layer and the
like can be produced by coating a coating liquid obtained by
dissolving the foregoing components into a solvent on the support
for the lithographic printing plate.
Cited as solvents used herein are ethylene dichloride,
cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol,
ethylene glycol monomethyl ether, 1-methoxy-2-propanol,
2-methoxyethyl acetate, 1-methoxy-2-propyl acetate,
dimethoxyethane, methyl lactate, ethyl lactate, N,
N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea,
N-methylpyrrolidone, dimethyl sulfoxide, sulfolan,
.gamma.-butyrolactone, toluene, water and the like. However, the
present invention is not limited to this. These solvents are used
singly or mixedly.
It is preferable that the concentration of the foregoing components
(entire solid part) in the solvent range from 1 to 50 wt %.
Various coating methods can be used. For example, bar coater
coating, rotation coating, spray coating, curtain coating, dip
coating, air knife coating, blade coating, roll coating and the
like can be cited.
[Method of Producing a Lithographic Printing Plate]
The presensitized plate of the present invention is made into a
lithographic printing plate by various treatment methods in
accordance with the kind of the image recording layer.
In general, image exposure is carried out. Cited as light sources
of active rays for use in the image exposure are, for example, a
mercury lamp, a metal halide lamp, a xenon lamp and a chemical
lamp. As laser beams, for example, helium-neon (He--Ne) laser,
argon laser, krypton laser, helium-cadmium laser, KrF excimer
laser, semiconductor laser, YAG laser and YAG-SHG laser are
cited.
When the image recording layer is of any of the thermal types, the
conventional types and the photopolymer type, it is preferable that
the presensitized plate is developed by use of a developer after
the exposure to obtain the lithographic printing plate. Although a
preferable developer for use in the presensitized plate of the
present invention is not particularly limited as long as the
developer is an alkali developer, an alkali aqueous solution that
does not substantially contain an organic solvent is preferable.
Moreover, the development can be carried out by use of a developer
that does not substantially contain alkali metal silicate. The
developing method using the developer that does not substantially
contain the alkali metal silicate is described in detail in JP
11-109637 A, and the contents described in JP 11-109637 A can be
used. Moreover, the presensitized plate of the present invention
can be developed by use of a developer that contains the alkali
metal silicate.
Above all, one of preferred aspects includes a method of producing
a lithographic printing plate (processing method) according to the
present invention where a lithographic printing plate is obtained
by performing a development with a developer containing
substantially no alkali metal silicates after a presensitized plate
of the present invention is exposed if an image recording layer is
either of thermal positive type, conventional positive type or
photopolymer type. Described below is a method of producing a
lithographic printing plate according to the present invention.
A method of producing a lithographic printing plate according to
the present invention is characterized by developing a
presensitized plate according to the present invention with a
developer containing substantially no alkali metal silicates.
If a presensitized plate according to the present invention is
developed with a developer containing substantially no alkali metal
silicates after exposed although alkali metal silicate treatment is
not performed on a support for a lithographic printing plate, a
lithographic printing plate excellent in scum resistance after
being left can be obtained. Moreover, it is acceptable that alkali
metal silicate treatment is performed on the support for a
lithographic printing plate.
In addition, there are no problems that non-image areas is whitened
and scum or sludge generates at the time of development since a
developer used contains substantially no alkali metal silicates
with a method of producing a lithographic printing plate according
to the present invention.
Moreover, a method of performing a development with a developer
containing substantially no alkali metal silicates is described in
detail in JP 11-109637 A and the contents described in JP 11-109637
A can be used in the present invention.
Although a preferred developer used in a method of producing a
lithographic printing plate according to the present invention is
not particularly limited as long as the developer contains
substantially no alkali metal silicates, it is preferable that it
is an alkali aqueous solution containing substantially no organic
solvent. However, it may contain an organic solvent as
required.
In addition, it is preferable that this developer contains
saccharaides. For example, cited is a developer that has at least
one compound selected from non-reducing sugar and at least one kind
of base, as principal components and that is at 9.0 to 13.5 pH.
Furthermore, a developer can contain various surfactants to promote
development property, diffuse development scum and improve ink
receptivity in the image areas of a lithographic printing plate as
required. In the present invention, either of anionic surfactant,
cationic surfactant, nonionic surfactant or amphoteric surfactant
can be used. In addition, a developer can contain various
development stabilizers. Moreover, a developer can also contain a
reducing agent to prevent a lithographic printing plate from being
scummed. Especially, it is effective to develop a presensitized
plate having a negative type photosensitive layer containing a
photosensitive diazonium chloride compound. In addition, a
developer can contain an organic carboxylic acid.
The contents of literatures cited herein are incorporated herein by
reference in its entirety.
EXAMPLE
Although the present invention will be described in detail with
reference to examples, the present invention is not limited to
these examples.
<Example of the First Aspect According to the Present
Invention>
1-1. Preparation of Support for a Lithographic Printing Plates
Example 1-1
<Aluminum Plate>
Molten metal was prepared by using an aluminum alloy containing Si:
0.06 wt %, Fe: 0.30 wt %, Cu: 0.005 wt %, Mn: 0.001 wt %, Mg: 0.001
wt %, Zn: 0.001 wt % and Ti: 0.03 wt %, and containing Al and
inevitable impurities for the remaining portion. After molten metal
treatment and filtering were performed, an ingot having a thickness
of 500 mm and a width of 1200 mm was made by a DC casting method.
After the surface was chopped to have an average thickness of 10 mm
with a surface chipper, the ingot was held at 550.degree. C. for
about 5 hours for soaking. When the temperature dropped to
400.degree. C., the ingot was formed into a rolled plate having a
thickness of 2.7 mm by using a hot rolling mill. Further, after the
heat treatment was performed at 500.degree. C. with a continuous
annealing machine, the roller plate was finished into an aluminum
plate having a thickness of 0.24 mm with cold rolling to obtain an
aluminum plate of JIS 1050 material. This aluminum plate was
processed to have a width of 1030 mm, and surface treatment
described below was continuously carried out.
<Surface Treatment>
Various surface treatments of (b) to (j) mentioned below were
continuously performed. Furthermore, a liquid squeezing was
performed by a nip roller after each treatment and water
washing.
(b) Alkali Etching Treatment
Etching treatment was performed on the aluminum plate obtained in
the foregoing manner by spraying an aqueous solution containing 2.6
wt % of sodium hydroxide and 6.5 wt % of aluminum ion at a
temperature of 70.degree. C. and the aluminum plate was dissolved
by 6 g/m.sup.2. After that, washing was performed by spraying
water.
(c) Desmutting Treatment
The aluminum plate was subjected to spray desmutting treatment in
aqueous solution of nitric acid 1 wt % (containing 0.5 wt % of
aluminum ions) at 30.degree. C., and then washed by spraying water.
For the aqueous solution of nitric acid used in the desmutting
treatment, waste solution generated in a process of electrochemical
graining treatment carried out by using an alternating current in
an aqueous solution of nitric acid to be described later was
utilized.
(d) Electrochemical Graining Treatment
Electrochemical graining treatment was continuously performed by
using an alternating current voltage of 60 Hz. Electrolyte in this
case was aqueous solution of nitric acid 10.5 g/L (containing 5 g/L
of aluminum ion and 0.007 wt % of ammonium ion) at a temperature of
50.degree. C. An alternating current supply waveform was like that
shown in FIG. 2. With the time TP necessary for a current value to
reach its peak from zero set as 0.8 msec, and duty ratio set at
1:1, and by using a trapezoidal wave, the electrochemical graining
treatment was performed while a carbon electrode was set as a
counter electrode. A ferrite was used for an auxiliary anode. An
electrolytic cell used is shown in FIG. 3.
The current density was 30 A/dm.sup.2 at a current peak value. The
total of the quantity of electricity was 220 C/dm.sup.2 when the
aluminum plate was at the anode side. An amount equivalent to 5% of
a current flowing from the power supply was shunted to an auxiliary
anode.
The aluminum plate was then washed by spraying water.
(e) Alkali Etching Treatment
Etching treatment was performed on an aluminum plate by straying an
aqueous solution containing 26 wt % of sodium hydroxide and 6.5 wt
% of aluminum ion at 32.degree. C. The aluminum plate was dissolved
by 0.25 g/m.sup.2, a smut component mainly containing aluminum
hydroxide generated in the previous stage of the electrochemical
graining treatment performed by using alternating current was
removed, and edge portions of formed pits were dissolved to be made
smooth. Then, the aluminum plate was washed by spraying water.
(f) Desmutting Treatment
The aluminum plate was subjected to spray desmutting treatment in
aqueous solution of nitric acid 15 wt % (containing 4.5 wt % of
aluminum ions) at 30.degree. C., and then washed by spraying water.
For the aqueous solution of nitric acid used in the desmutting
treatment, waste solution generated in the process of the
electrochemical graining treatment carried out by using an
alternating current of a nitric acid was utilized.
(g) Electrochemical Graining Treatment
Electrochemical graining treatment was continuously performed by
using an alternating current voltage of 60 Hz. Electrolyte in this
case was aqueous solution of hydrochloric acid 7.5 g/L (containing
5 g/L of aluminum ion) at a temperature of 35.degree. C. An
alternating current supply waveform was like that shown in FIG. 2.
With the time TP necessary for a current value to reach its peak
from zero set as 0.8 msec, and duty ratio set at 1:1, and by using
a trapezoidal wave, the electrochemical graining treatment was
performed while a carbon electrode was set as a counter electrode.
A ferrite was used for an auxiliary anode. An electrolytic cell
used is shown in FIG. 3.
The current density was 25 A/dm.sup.2 at a current peak value. The
total of the quantity of electricity was 50 C/dm.sup.2 when the
aluminum plate was at the anode side Then, the aluminum plate was
washed by spraying water.
(h) Alkali Etching Treatment
Etching treatment was performed on an aluminum plate by straying an
aqueous solution containing 26 wt % of sodium hydroxide and 6.5 wt
% of aluminum ion at 32.degree. C. The aluminum plate was dissolved
by 0.1 g/m.sup.2, a smut component mainly containing aluminum
hydroxide generated in the previous stage of the electrochemical
graining treatment performed by using alternating current was
removed, and edge portions of formed pits were dissolved to be made
smooth. Then, the aluminum plate was washed by spraying water.
(i) Desmutting Treatment
The aluminum plate was subjected to spray desmutting treatment in
aqueous solution of sulfuric acid 25 wt % (containing 0.5 wt % of
aluminum ions) at 60.degree. C., and then washed by spraying
water.
(j) Anodizing Treatment
By using anodizing device with a structure shown in FIG. 4,
anodizing treatment was carried out. Accordingly, a support for a
lithographic printing plate according to Example 1-1 was obtained.
Electrolyte supplied for each of first and second electrolytic
portions was sulfuric acid. For each electrolyte, the concentration
of sulfuric acid was 170 g/L (containing 0.5 wt % of aluminum ion)
at a temperature of 38.degree. C. Then, washing by spraying water
was carried out. The final amount of an anodized layer was 2.7
g/m.sup.2.
Examples 1-2 and 1-3
Supports for a lithographic printing plate according to Examples
1-2 and 1-3 were obtained with the same method as in Example 1-1,
except that the amounts of the aluminum plate dissolved were 0.2
g/m.sup.2 and 0.5 g/m.sup.2, respectively, in (h) mentioned
above.
Example 1-4
A support for a lithographic printing plate according to Example
1-4 was obtained with the same method as in Example 1-1, except
that the frequency of an alternating current voltage was set at 30
Hz in (g) mentioned above, and (h) mentioned above was not
performed.
Examples 1-5 and 1-6
Supports for a lithographic printing plate according to Examples
1-5 and 1-6 were obtained with the same method as in Example 1-1,
except that the frequency of an alternating current voltage were
set at 300 Hz and 500 Hz, respectively, in (g) mentioned above.
Example 1-7
A support for a lithographic printing plate according to Example
1-7 was obtained with the same method as in Example 1-1, except
that the current density was set 15 A/dm.sup.2 at a current peak
value in (d) mentioned above.
Example 1-8
A support for a lithographic printing plate according to Example
1-8 was obtained with the same method as in Example 1-1, except
that the temperature of an electrolyte was set at 70.degree. C. in
(d) mentioned above
Examples 1-9 to 1-13
Supports for a lithographic printing plate according to Examples
1-9 to 1-13 were obtained with the same methods as in Examples 1-1,
1-4, 1-5, 1-7 and 1-8, except that (a) to be mentioned below were
performed before (b) mentioned above.
(a) Mechanical Graining Treatment
Mechanical graining treatment was carried out by rotating roller
nylon brushes while supplying suspension containing abrasive
(pumice) and water (specific gravity: 1.12) as abrasive slurry
liquid to the surface of the aluminum plate, using device shown in
FIG. 1. In FIG. 1, 1 represents an aluminum plate, 2 and 4
represent roller brushes, 3 represents an abrasive slurry liquid,
and 5, 6, 7 and 8 represent supporting rollers. The abrasive had
average particle size of 40 .mu.m and the maximum particle size of
100 .mu.m. A material for the nylon brush was 6.cndot.10 nylon,
having a bristle length of 50 mm, and a bristle diameter of 0.3 mm.
The Nylon brush was made by boring holes in a .phi.300 mm stainless
cylinder and densely implanting bristles therein. Three of such
rotary brushes were prepared. Each distance between two supporting
rollers (.phi.200 mm) in the lower part of the brush was 300 mm.
Each brush roller was pressed until a load of a driving motor for
rotating the brush reached plus 7 kW with respect to the load
before the brush roller was pressed to the aluminum plate. The
rotating direction of each brush was the same as the moving
direction of the aluminum plate. The number of rotations of the
brushes was 200 rpm.
Example 1-14
A support for a lithographic printing plate according to Example
1-14 was obtained with the same method as in Example 1-9, except
that an abrasive was silica sand in (a) mentioned above.
Example 1-15
A support for a lithographic printing plate according to Example
1-15 was obtained with the same methods as in Example 1-14, except
that the number of rotations of the brushes was 100 rpm in (a)
mentioned above.
Example 1-16
A support for a lithographic printing plate according to Example
1-16 was obtained with the same method as in Example 1-1, except
that (z) to be described below was performed before (b) mentioned
above.
(z) Honing Treatment
Asperities were provided by pressurizing water in which iron balls
of diameter 100 .mu.m were suspended, thereby jetting the water
onto the surface of the aluminum plate.
Example 1-17
A support for a lithographic printing plate according to Example
1-17 was obtained with the same methods as in Example 1-9, except
that an internationally registered alloy 3103 material was used in
place of JIS 1050 material.
Comparative Example 1-1
A support for a lithographic printing plate according to
Comparative Example 1-1 was obtained with the same method as in
Example 1-3, except that the frequency of alternating current
voltage was set at 10 Hz in (g) mentioned above.
Comparative Example 1-2
A support for a lithographic printing plate according to
Comparative Example 1-2 was obtained with the same method as in
Example 1-1, except that the frequency of alternating current
voltage was set at 10 Hz in (g) mentioned above and the amount of
the aluminum plate dissolved was set at 1.0 g/m.sup.2 in (h)
mentioned above.
Comparative Example 1-3
A support for a lithographic printing plate according to
Comparative Example 1-3 was obtained with the same method as in
Example 1-1, except that the frequency of alternating current
voltage was set at 15 Hz in (d) mentioned above.
Comparative Example 1-4
A support for a lithographic printing plate according to
Comparative Example 1-4 was obtained with the same method as in
Example 1-1, except that the temperature of an electrolyte was set
at 80.degree. C. and TP was set at 0 msec. in (d) mentioned
above.
Comparative Example 1-5
A support for a lithographic printing plate according to
Comparative Example 1-5 was obtained with the same method as in
Example 1-8, except that the frequency of alternating current
voltage was set at 10 Hz in (g) mentioned above and the amount of
the aluminum plate dissolved was set at 1.0 g/m.sup.2 in (h)
mentioned above.
Comparative Example 1-6
A support for a lithographic printing plate according to
Comparative Example 1-6 was obtained with the same method as in
Example 1-9, except that (g), (h) and (i) mentioned above were not
performed.
Comparative Example 1-7
A support for a lithographic printing plate according to
Comparative Example 1-7 was obtained with the same method as in
Example 1-1, except that (g), (h) and (i) mentioned above were not
performed.
Comparative Example 1-8
A support for a lithographic printing plate according to
Comparative Example 1-8 was obtained with the same method as in
Example 1-1, except that (d), (e) and (f) mentioned above were not
performed and the total quantity of electricity when the aluminum
plate was at the anode side was set at 500 C/dm.sup.2.
Comparative Examples 1-9 and 1-10
Supports for a lithographic printing plate according to Comparative
Examples 1-9 and 1-10 were obtained with the same method as in
Comparative Example 1-8, except that the amounts of the aluminum
plates dissolved were set at 0.2 g/m.sup.2 and 0.5 g/m.sup.2,
respectively, in (h) mentioned above.
Comparative Example 1-11
A support for a lithographic printing plate according to
Comparative Example 1-11 was obtained with the same method as in
Example 1-9, except that (d), (e), (f), (g), (h) and (i) mentioned
above were not performed.
Comparative Example 1-12
A support for a lithographic printing plate according to
Comparative Example 1-12 was obtained with the same method as in
Example 1-1, except that (d), (e) and (f) mentioned above were not
performed.
Comparative Example 1-13
A support for a lithographic printing plate according to
Comparative Example 1-13 was obtained with the same method as in
Example 1-9, except that (d), (e) and (f) mentioned above were not
performed.
Comparative Example 1-14
A support for a lithographic printing plate according to
Comparative Example 1-14 was obtained with the same method as in
Comparative Example 1-9, except that a mixture of hydrochloric acid
and acetic acid (hydrochloric acid concentration: 7.5 g/L and
acetic acid concentration: 15 g/L) as an electrolyte was used in
(g) mentioned above. 1-2. Measurement of surface shape of a support
for a lithographic printing plate
For concave portions of the surface of each of the supports for a
lithographic printing plate obtained as mentioned above,
measurement of the (1) to (4) as below were performed.
The results were shown in Table 1. Note that, "-" in the table 1
indicates that there was no concave portion in the corresponding
wavelength.
(1) Average Aperture Diameter of a Grained Structure with Medium
Undulation
The surface of the support was photographed at a magnification of
2,000 from right above with an SEM. Next, in SEM micrograph
obtained, 50 pits of a grained structure with medium undulation
(pits of medium undulation) in which circumferences of the pits
were annularly connected were extracted, aperture diameters were
determined by reading the diameters of the pits, and an average
diameter aperture was calculated. (2) Average Aperture Diameter of
a Grained Structure with Small Undulation
The surface of the support for a lithographic printing plate was
photographed at a magnification of 50,000 from right above with an
SEM. In an SEM micrograph obtained, 50 pits of the grained
structure with small undulation (pits of small undulation) were
extracted, the aperture diameter was determined by reading the
diameters of the pits and an average aperture diameter was
calculated.
(3) Average of Ratio of Depth with Respect to the Aperture Diameter
of a Grained Structure with Small Undulation
The average of ratio of depth with respect to aperture diameter of
a grained structure with small undulation was obtained as follows.
A broken-out section of the support was photographed at a
magnification of 50,000 with a high resolution SEM. In an SEM
micrograph obtained, 20 pits of small undulation with aperture
diameter 0.3 .mu.m or less were extracted, the ratios were obtained
by reading the aperture diameters and depths, and an average ratio
was calculated.
(4) Average Wavelength of a Grained Structure with Large
Undulation
A two-dimensional roughness measurement was performed with a stylus
type surface roughness gauge (sufcom576 made by Tokyo Seimitsu Co.,
Ltd.), a mean spacing of peaks S.sub.m specified in ISO4287 was
measured five times, and its mean value was determined to be an
average wavelength. The two-dimensional roughness measurement was
performed under the following conditions.
Cut off: 0.8 .mu.m, gradient correction: FLAT-ML, measured length:
3 mm, depth magnification: 10,000, scanning speed: 0.3 mm/sec., and
sensing pin diameter: 2 .mu.m.
1-3. Preparation of Presensitized Plates
Each of presensitized plates was obtained by providing either of
the following three kinds of image recording layers in combinations
as shown in Table 1 on each support for a lithographic printing
plate obtained as mentioned above.
(1) Conventional Positive Type Image Recording Layer
Undercoat solution containing a composition described below was
coated on the support for a lithographic printing plate, obtained
in the foregoing manner, and dried at a temperature of 80.degree.
C. for 30 sec, to form a coating layer of undercoat layer. The
coating amount after drying was 10 mg/m.sup.2.
<Composition of Undercoat Solution>
TABLE-US-00002 Dihydroxyethylglycine 0.05 parts by weight Methanol
94.95 parts by weight Water 5.00 parts by weight
Photosensitive resin solution containing a composition described
below was coated on the undercoat layer, and dried at a temperature
of 100.degree. C. for 2 min., to form a photosensitive layer
(conventional positive type image recording layer) and a
presensitized plate was obtained. The coating amount after drying
was 2.5 g/m.sup.2.
<Composition of Photosensitive Resin Solution>
TABLE-US-00003 Ester of naphtoquinone-1,2-dyazide-5- 0.73 g
sulfonylchloride and pyrogallol-acetone resin Cresol-novolac resin
2.00 g Dye (Oil Blue #603 made by Orient Chemical 0.04 g
Industries, Ltd.) Ethylene dichloride 16 g 2-methoxyethylacetate 12
g
(2) Thermal Positive Type Image Recording Layer
Alkali metal silicate treatment (silicate treatment) was carried
out by dipping the support for a lithographic printing plate,
obtained as described above, into a treatment cell with the aqueous
solution containing 1 wt % of III-sodium silicate at a temperature
of 30.degree. C. for 10 sec. Then, the support was washed by water
spraying using well water.
Undercoat solution containing a composition described below was
coated on the support for a lithographic printing plate treated
with the alkali metal silicate, obtained in the foregoing manner,
and dried at a temperature of 80.degree. C. for 15 sec., to form a
coating layer. The coating amount after drying was 10
mg/m.sup.2.
<Composition of Undercoat Solution>
TABLE-US-00004 High-molecular compound described below 0.2 g
Methanol 100 g Water 1 g ##STR00001## ##STR00002##
Subsequently, thermosensitive layer coating solution having a
composition described below was prepared and, the thermosensitive
coating solution was coated over the undercoated support for a
lithographic printing plate, so that the amount after drying (the
coating amount of thermosensitive layer) meets 1.7 g/m.sup.2. Then,
drying was carried out in order to form thermosensitive layer
(thermal positive type image recording layer). In this way, the
presensitized plate was obtained.
<Composition of Thermosensitive Layer Coating Solution>
TABLE-US-00005 Novolac resin (m-cresol/p-cresol = 60/40, weight-
1.0 g average molecular weight 7,000, unreacted cresol 0.5 wt %
contained) Cyanine dye A expressed by the following structural 0.1
g formula Tetrahydro phthalic anhydride 0.05 g p-toluensulfonic
acid 0.002 g A compound formed by converting a counterion of 0.02 g
ethylviolet into 6-hydroxy-.beta.-naphthalenesulfonic acid
Fluorine-containing surfactant (Megaface F-177 made 0.05 g by
Dainippon Ink And Chemical, Incorporated) Methylethylketone 12
g
##STR00003##
(3) Photopolymer Type Image Recording Layer
Solution that a polymer expressed by the following formula U-1
(number-average molecular weight: 10,000) was dissolved in a
mixture solution of water/methanol-5/95 (weight ratio) was coated
onto the support for a lithographic printing plate obtained above,
and an undercoat layer (adhesive layer) was formed by drying the
support at 80.degree. C. for 30 seconds (Sol-Gel undercoat). The
coating amount of an undercoat layer after drying was 10
mg/m.sup.2.
U-1
##STR00004##
Furthermore, the high-sensitivity photopolymerizable composition
P-1 of the following constitution was prepared, this composition
was applied to the undercoated support for a lithographic printing
plate such that a coated amount after being dried (coated amount of
photosensitive layer) becomes 1.5 g/m.sup.2, a photosensitive layer
was formed by drying the support at 100.degree. C. for one
minute.
<Photopolymerizable Composition P-1>
TABLE-US-00006 Compound containing ethylenic unsaturated bond 1.5
parts by weight expressed by the following formula A1 Linear
organic polymer (high-molecular binder) 2.0 parts by weight
expressed by the following formula B1 Sensitizer expressed by the
following formula C1 0.15 parts by weight Photopolymeric initiator
expressed by the following 0.2 parts by weight formula D1 Dispersed
substance of .epsilon.-phthalocyanine 0.02 parts by weight
expressed by the following formula F1 Fluorine-containing nonionic
surfactant (Megaface 0.03 parts by weight F-177 made by Dainippon
Ink And Chemicals, Incorporated) Methylethylketone 9.0 parts by
weight Propyleneglycol monomethylether acetate 7.5 parts by weight
Toluene 11.0 parts by weight
##STR00005## ##STR00006##
An aqueous solution of polyvinyl alcohol (degree of saponification
98 mol %, degree of polymerization 500) 3 wt % was coated onto this
photosensitive layer such that a coated amount after drying meets
2.5 g/m.sup.2, a photosensitive layer (photopolymer negative type
image recording layer) was formed by drying the support at
120.degree. C. for 3 min. and thus, a presensitized plate was
obtained.
1-4. Exposure and Development Treatment
Image exposure and development treatment were performed on each
presensitized plate obtained above in the following methods
corresponding to image recording layers and a lithographic printing
plate was obtained.
(1) In a case of Conventional Positive Type Image Recording
Layer
Exposure was performed on a presensitized plate with a 3 kW metal
halide lamp from a distance 1 meter away through a transparent
positive film in a vacuum printing frame.
Thereafter, development treatment was performed with an alkali
developer (developer 1) in which the following compound (a) was
added to an aqueous solution 1L containing 4.0 wt % of potassium
silicate of the mixing ratio of silicon oxide SiO.sub.2 and
potassium oxide K.sub.2O, SiO.sub.2/K.sub.2O was 1:1 and 0.015 wt %
of OLFINE AK-02 (made by Nissin Chemical Industry Co., Ltd.) such
that the concentration of the compound (a) is 1.0 g/L. Development
treatment was performed at a development temperature of 25.degree.
C. for 12 seconds with an automatic processor PS900NP (made by Fuji
Photo Film Co., Ltd.) filled with the aforementioned developer 1.
After the development treatment was finished, treatment with gum
(GU-7 (1:1) or the like was performed on the plate after water
washing treatment was performed, and a lithographic printing plate
with plate making completed was obtained. Note that, in place of
the compound (a), even when an alkali developer containing the same
addition of the following compound (b) or (c) as that of the
compound (a) was used, development treatment could be performed in
the same manner (and same in each of the Examples mentioned
below).
<Compounds (a) to (c)>
Compound (a): C.sub.12H.sub.25N (CH.sub.2CH.sub.2COONa).sub.2
Compound (b): C.sub.12H.sub.25O (CH.sub.2CH.sub.2O).sub.7H
Compound (c):
(C.sub.6H.sub.13).sub.2CHO(CH.sub.2CH.sub.2O).sub.20H
(2) In a Case of Thermal Positive Type Image Recording Layer
Image exposure was performed on a presensitized plate at a main
scanning speed of 5 m/sec and printing plate energy of 140
mJ/cm.sup.2, with CREO Inc.-made TrendSetter 3244 equipped with a
semiconductor laser of output 500 mW, wavelength 830 nm and beam
diameter 17 .mu.m (1/e.sup.2).
Thereafter, development treatment was performed on the
presensitized plate with an alkali developer (developer 2) in which
the compound (a) was added to an aqueous solution IL containing 5.0
wt % of potassium salt having D-sorbitol/potassium oxide K.sub.2O
which was a combination of non-reducing sugar and base and OLFINE
AK-02 (made by Nissin Chemical Industry Co., Ltd.) 0.015 wt %. This
treatment was performed at a development temperature of 25.degree.
C. for 12 seconds with an automatic processor PS900NP (made by Fuji
Photo Film Co., Ltd.) filled with the aforementioned developer 2.
After the development treatment was over, water washing treatment
was then performed, treatment with gum (GU-7 (1:1)) or the like was
performed, and a lithographic printing plate with plate making
completed was obtained.
(3) In a case of Photopolymer Type Image Recording Layer
Scanning exposure of a solid image and 1 to 99% dot image (in every
1%) was performed on the presensitized plate at an exposure amount
of 100 .mu.J/cm.sup.2 and 175 scanning lines/inch at 4,000 dpi with
FD.YAG laser (Plate Jet 4 made by Cymbolic Sciences, Inc.). After
exposure, preheating was performed under a condition that a
printing plate reached a temperature of 100.degree. C.
Standard treatment was then performed with an automatic processor
(LP-850P2 made by Fuji Photo Film Co., Ltd.) filled with developer
3 of the following composition (pH 11.5 (at 25.degree. C.) and
electric conductivity 5 mS/cm) and finishing gum solution FP-2W
(made by Fuji Photo Film Co., Ltd.). The temperature of the
developer was 30.degree. C., and the dipping time in the developer
was about 15 seconds.
<Compositions of Developer 3>
TABLE-US-00007 Potassium hydroxide 0.15 g
Polyoxyethylenephenylether (number of 5.0 g constitutional
repeating unit of polyoxyethylene chain: n = 13) Chelating agent
(Chelest 400 made by Chelest 0.1 g Corporation) Water 94.75 g
1-5. Evaluation of a Lithographic Printing Plate
Scum resistance, scum resistance after being left, press life and
easiness to observe amount of fountain solution of the
presensitized plate obtained above were evaluated according to the
following methods.
(1) Scum Resistance
Printing was performed in magenta ink of DIC-GEOS (s) with
DAIYA-F-2 printing machine (made by Mitsubishi Heavy Industries,
Ltd.) and the scum of a blanket was visually inspected after a
printing of 10,000 sheets was carried out.
The results were shown in Table 1. Scum resistance was evaluated in
ten levels according to the level of scum in the blanket. A larger
number shows a better excellency in scum resistance.
(2) Scum Resistance After Being Left
In the evaluation of the aforementioned scum resistance, after a
printing of 10,000 sheets was finished, they were left as they
stand for one hour. After that, a printing was restarted and the
scum of the blanket in the non-image areas was visually
inspected.
The results were shown in Table 1. Scum resistance after being left
was evaluated in four levels of .circleincircle., .smallcircle.,
.DELTA., and .times. from the order of a lesser extent of scum in
the blanket.
(3) Press Life
Printing was performed in black ink of DIC-GEOS (N) made by
Dainippon Ink And Chemicals, Incorporated with Lithrone Printing
Machine made by Komori Corporation, and press life was evaluated by
the number of the printed sheets at a time when a visual inspection
recognizes that the density of a solid image begins to
decrease.
The results were shown in Table 1.
(4) Inspectability of Plate
The lithographic printing plate obtained was mounted on the
Lithrone Printing Machine made by Komori Corporation, the luster of
non-image areas on the surface of a printing plate was visually
observed while increasing the supplied amount of fountain solution,
and the inspectability of a plate (easiness to observe amount of
fountain solution) was evaluated by the supplied amount of fountain
solution when the non-image areas began to luster.
The results were shown in Table 1. The inspectability was evaluated
in three-steps in the order of .circleincircle., .DELTA., and
.times. from non-image areas with a larger amount of fountain
solution to that with a lesser amount of fountain solution when
non-image areas began to luster.
As is clear from Table 1, a presensitized plate according to the
present invention using a support for a lithographic printing plate
of the first aspect according to the present invention (Examples
1-1 to 1-17), having on the surface thereof, a grain shape with a
structure in which a grained structure with medium undulation of a
specified aperture diameter and a grained structure with small
undulation of a specified aperture diameter were superimposed was
excellent in both scum resistance and press life when the plate was
formed into a lithographic printing plate. Particularly, the depth
with respect to the aperture diameter of a small undulation pit was
sufficiently deep (Examples 1-1, 1-2 and 1-4 to 1-17), a plate was
excellent in scum resistance.
In addition, if a grained structure with large undulation of a
specified wavelength was further superimposed on the aforementioned
grain shape (Examples 1-9 to 1-15 and 1-17), a lithographic
printing plate was also excellent in both inspectability and scum
resistance after being left.
On the contrary, if the average aperture diameter of small
undulation pits was too large (Comparative Examples 1-1, 1-2 and
1-5), a plate was inferior in scum resistance. In addition, if the
average aperture diameter of medium undulation pits was too large
(Comparative Example 1-3) or was too small (Comparative Example
1-4), a plate was inferior in both scum resistance and press life.
Furthermore, the average aperture diameters of both small
undulation pits and medium undulation pits were too large
(Comparative Example 1-14), a plate was inferior in press life.
Moreover, if a plate was not provided with a grained structure with
small undulation (Comparative Examples 1-6, 1-7 and 1-11), the
plate was poor in scum resistance and if a plate was not provided
with a grained structure with medium undulation (Comparative
Examples 1-8 to 1-13), the plate was inferior in press life.
TABLE-US-00008 TABLE 1 Image recording layer Interface treatment of
support Surface shape of support Conventional positive type Large
Medium Small None undulation Undulation undulation Scum Average
Average Average Average of ratios resistance Press life wavelength
aperture diameter aperture diameter of depths to Scum after being
(10 thousand Inspectability of (.mu.m) (.mu.m) (.mu.m) aperture
diameters resistance left pieces) plate Example 1-1 -- 1.4 0.14
0.46 10 .largecircle. 11.0 .DELTA. Example 1-2 -- 1.4 0.16 0.22 8
.largecircle. 11.0 .DELTA. Example 1-3 -- 1.4 0.15 0.16 8
.largecircle. 12.0 .DELTA. Example 1-4 -- 1.4 0.18 0.22 8
.largecircle. 10.0 .DELTA. Example 1-5 -- 1.4 0.07 0.22 7
.largecircle. 11.0 .DELTA. Example 1-6 -- 1.4 0.03 0.30 8
.largecircle. 10.0 .DELTA. Comparative -- 1.4 0.25 0.20 6
.largecircle. 11.0 .DELTA. Example 1-1 Comparative -- 1.4 0.25 0.12
5 .largecircle. 11.0 .DELTA. Example 1-2 Example 1-7 -- 3.5 0.14
0.46 8 .largecircle. 9.0 .DELTA. Example 1-8 -- 1.0 0.14 0.46 8
.largecircle. 10.0 .DELTA. Comparative -- 5.6 0.14 0.46 4
.largecircle. 9.0 .DELTA. Example 1-3 Comparative -- 0.4 0.14 0.46
6 .largecircle. 10.0 .DELTA. Example 1-4 Example 1-9 65 1.4 0.14
0.46 10 .circleincircle. 10.0 .largecircle. Example 1-10 65 1.4
0.18 0.22 8 .largecircle. 10.0 .largecircle. Example 1-11 65 1.4
0.07 0.22 7 .largecircle. 10.0 .largecircle. Comparative 65 1.4
0.25 0.12 5 .largecircle. 8.0 .largecircle. Example 1-5 Example
1-12 65 3.5 0.14 0.46 8 .largecircle. 10.0 .largecircle. Example
1-13 65 1.0 0.14 0.46 8 .largecircle. 9.0 .largecircle. Example
1-14 37 3.5 0.14 0.46 8 .circleincircle. 11.0 .largecircle. Example
1-15 14 1.4 0.14 0.46 7 .circleincircle. 10.0 .largecircle. Example
1-16 120 3.5 0.14 0.46 8 .circleincircle. 9.0 .DELTA. Example 1-17
79 3.5 0.14 0.46 10 .circleincircle. 13.0 .largecircle. Comparative
70 1.6 -- -- 6 .largecircle. 8.0 .largecircle. Example 1-6
Comparative -- 1.4 -- -- 2 .largecircle. 10.0 .DELTA. Example 1-7
Comparative 51 -- 0.25 0.46 8 .largecircle. 6.0 .largecircle.
Example 1-8 Comparative 51 -- 0.25 0.22 9 .largecircle. 4.0
.largecircle. Example 1-9 Comparative 51 -- 0.25 0.14 9
.largecircle. 3.0 .largecircle. Example 1-10 Comparative 60 -- --
-- 2 .largecircle. 8.0 .largecircle. Example 1-11 Comparative -- --
0.14 0.46 10 .DELTA. 0.5 X Example 1-12 Comparative 65 -- 0.14 0.46
6 X 7.0 .largecircle. Example 1-13 Comparative -- 5.8 0.25 0.26 9
.largecircle. 5.0 .largecircle. Example 1-14 Thermal positive type
Photopolymer type Silicate treatment None Press life Press life
Scum (10 thousand Scum (10 thousand resistance pieces) resistance
pieces) Example 1-1 10 8.0 10 20.0 Example 1-2 Example 1-3 Example
1-4 8 8.0 Example 1-5 Example 1-6 Comparative 6 9.0 Example 1-1
Comparative Example 1-2 Example 1-7 Example 1-8 8 8.0 Comparative
Example 1-3 Comparative 6 3.0 Example 1-4 Example 1-9 10 10.0 10
18.0 Example 1-10 8 9.0 Example 1-11 Comparative Example 1-5
Example 1-12 8 9.0 Example 1-13 Example 1-14 Example 1-15 7 9.0
Example 1-16 Example 1-17 Comparative 6 6.0 6 10.0 Example 1-6
Comparative 2 8.0 2 16.0 Example 1-7 Comparative 8 4.0 8 14.0
Example 1-8 Comparative Example 1-9 Comparative Example 1-10
Comparative 2 6.0 2 8.0 Example 1-11 Comparative 10 0.5 10 0.5
Example 1-12 Comparative 6 5.0 6 12.0 Example 1-13 Comparative
Example 1-14
<Example of the Second Aspect According to the Present
Invention> 2-1. Preparation of a Support for a Lithographic
Printing Plate
Example 2-1
A support for a lithographic printing plate according to Example
2-1 was obtained in the same method as in Example 1-9, except that
the amount of an aluminum plate dissolved was set at 1.0 g/m.sup.2
in (e) mentioned above.
Examples 2-2 to 2-6 and Comparative Examples 2-1 to 2-11
Supports for a lithographic printing plate according to Examples
2-2 to 2-6 and Comparative Examples 2-1 to 2-11 were obtained in
the same methods as in Example 2-1, except that the conditions of
each treatment were changed as shown in Table 2. Note that, "-" in
Table 2 indicates that no treatment was performed. An electrolyte
used for (d) electrolytic graining treatment in Comparative Example
2-6 was a electrolyte in which the concentration of hydrochloric
acid was 1 wt % and that of acetic acid was 1 wt %. An electrolyte
used in Examples 2-4 and 2-5 and Comparative Example 2-3 was each a
solution in which aluminum ion concentration was 5 g/L.
2. Calculation of Factor of Surface Shape on a Support for a
Lithographic Printing Plate
With the surface of a support for a lithographic printing plate
obtained above, R.sub.a, .DELTA.S, a30 and a60 were taken as
follows:
The results were shown in Table 2.
(1) Measurement of Surface Shape with an Atomic Force
Microscope
The shape of a surface was measured with an atomic force microscope
(SP13700 made by Seiko Instruments Inc.) to find a
three-dimensional data. Described below are the concrete steps.
Measurement was performed on the following conditions. That is, 1
cm-square of the support for a lithographic printing plate was cut
off, the piece was set on a horizontal sample bench on a piezo
scanner, a cantilever was moved closer to the surface of the
sample, and when the cantilever reached an area where an atomic
force functions, the sample was scanned in XY directions. While
scanning, asperities of the sample were captured as piezo
displacement in Z direction.
A piezo scanner capable of scanning 150 .mu.m in XY directions and
10 .mu.m in Z direction was used. A cantilever with resonance
frequency of 120 to 150 kHz, and spring constant of 12 to 20 N/M
(e.g., S1-DF20 made by NANOPROBE Inc.) was used, and measurement
was performed in DFM mode (Dynamic Force Mode) A minor tilting of
the sample was corrected by least square approximation method of
the three-dimensional data obtained to find a reference plane.
A surface in 50 .mu.m.quadrature. area was measured at
512.times.512 points. The resolution in XY directions was 1.9
.mu.m, the resolution in Z direction was 1 nm, and scanning rate
should was 60 .mu.m/sec.
(2) Correction of Three-dimensional Data
While in the calculation of .DELTA.S, the three-dimensional data
found in (1) mentioned above was used as it was, in calculation of
R.sub.a, a30 and a60, a data that was corrected by removing
components of wavelength 2 .mu.m or longer from the
three-dimensional data taken in (1) mentioned above was
employed.
The correction was performed by performing the fast Fourier
transform of the three-dimensional data taken in (1) mentioned
above to find frequency distribution, and performing inverse
Fourier transform after removing components of wavelength 2 .mu.m
or longer.
(3) Calculation of each Factor
(i) R.sub.a
Surface roughness R.sub.a was calculated by the following equation
using the three-dimensional data (f (x, y)) obtained after a
correction was performed in (2) mentioned above.
.times..intg..times..intg..times..function..times..times.dd
##EQU00003##
In the equation, each of L.sub.x and L.sub.y indicates the length
of a side in x direction and y direction of a measured area
(rectangle) and their relation was that L.sub.x=L.sub.y=50 .mu.m in
the Example. In addition, S.sub.0 was a geometrically measured area
and was found by an equation that
S.sub.0=L.sub.x.times.L.sub.y.
(ii) .DELTA.S
Adjacent three points were extracted using the three-dimensional
data (f (x, y)) found in (1) mentioned above, and the total of
areas of fine triangles formed by the three points was found, which
was determined to be actual area S.sub.x. Surface area ratio
.DELTA.S was found by the following equation from the obtained
actual area S.sub.x and geometrically measured area S.sub.0:
.DELTA.S=(S.sub.x-S.sub.0)/S.sub.0.times.100(%)
(iii) a30 and a60
Using the three-dimensional data (f (x, y)) obtained by correction
in (2) mentioned above, an angle made between a reference plane and
a fine triangle formed by the three points constituted by each
reference point and adjacent two points in predetermined directions
(for example, rightwards and downwards) was calculated, for each
reference point. The number of reference points at which a gradient
of the fine triangle is 300 or more (in the case of a30) or
60.degree. or more (in the case of a60) was divided by the number
of all reference points (herein, the number of all reference points
was 511.times.511 points, that was obtained by subtracting the
number of points which did not have adjacent two points in the
predetermined directions from 512.times.512 points, that is, the
number of all data). Accordingly, an area ratio a30 of a portion of
gradient 30.degree. or more and an area ratio a60 of a portion of
gradient 60.degree. or more were calculated.
3. Preparation of a Presensitized Plate
A presensitized plate was obtained by providing either of a thermal
positive type image recording layer A or a conventional positive
type image recording layer B in the same methods as in the examples
of the first aspect according to the present invention on each
support for a lithographic printing plate obtained above.
4. Exposure and Development Treatment
Image exposure and development treatment were performed on each
support for a lithographic printing plate corresponding to an image
recording layer in the following manner and a lithographic printing
plate was obtained.
(1) In a Case of a Thermal Positive Type Image Recording Layer
Exposure and development treatment were performed in the same
method as in the examples of the first aspect according to the
present invention as mentioned above and a lithographic plate was
obtained.
(2) In a case of a Conventional Positive Type Image Recording
Layer
Exposure and development treatment were performed to obtain a
lithographic printing plate in the same method as in the examples
of the first aspect according to the present invention, except that
the aforementioned developer 2 was used in place of the
aforementioned developer 1.
5. Evaluation of a Lithographic Printing Plate
Scum resistance, press life, scum resistance after being left and
inspectability of plate of the lithographic printing plate were
evaluated in the following manner.
(1) Scum Resistance
Scum resistance was evaluated in the same method as in the examples
of the first aspect according to the present invention as mentioned
above.
The results were shown in Tables 3 and 4.
(2) Press Life
Press life resistance was evaluated in the same method as in the
examples of the first aspect according to the present invention as
mentioned above.
The results were shown in Tables 3 and 4. Note that press life was
expressed in relative value that the number of printed sheets with
a lithographic printing plate provided with image recording layer A
on a support for a lithographic printing plate in Example 2-5 was
determined to be 100.
(3) Scum Resistance After Being Left
Scum resistance after being left was evaluated in the same method
as in the examples of the first aspect according to the present
invention as mentioned above.
Note that, if image recording layer B was provided, the same
evaluation was performed with a lithographic printing plate on
which development treatment was performed under the same
conditions, except that developer 1 was used in place of developer
2 after the plate was exposed, for comparison.
The results were shown in Tables 3 and 4. Scum resistance after
being left was evaluated in 10 levels according to the extent of
scum in a blanket. A larger number indicates that a plate has
better scum resistance after being left.
(4) Inspectability of Plate
Inspectability of plate was evaluated in the same method as in the
examples of the first aspect according to the present invention as
mentioned above.
The results were shown in Table 3. A plate with a larger amount of
fountain solution to a smaller amount of fountain solution when the
plate was beginning to luster was evaluated in three-steps of
.smallcircle., .DELTA., and .times..
As apparent from Tables 3 and 4, a presensitized plate according to
the present invention using the support for a lithographic printing
plate of the second aspect according to the present invention, in
which R.sub.a, .DELTA.S, a30 and a60 obtained from the
three-dimensional data taken by measuring 512.times.512 points in
50 .mu.m-square on the surface of a plate with an atomic force
microscope each meets the specified conditions (Examples 2-1 to
2-6), was excellent in both scum resistance and press life when the
plate was formed into a lithographic printing plate. It was also
excellent in both scum resistance after being left and
inspectability of plate.
Particularly, Table 4 shows that when a support for a lithographic
printing plate on which no alkali metal silicate treatment was
performed was used (i.e., when image recording layer B was
provided), although development treatment was performed on the
plate with developer 2 containing substantially no alkali metal
silicate, it exerted scum resistance after being left equivalent to
a case if development treatment was performed on the plate with
developer 1 containing alkali metal silicate.
TABLE-US-00009 TABLE 2 Surface treatment (d) (e) (h) (a)
Electrolytic Alkali (g) Alkali Mechanical graining etching
Electrolytic etching graining treatment treatment graining
treatment treatment Electrolyte/ Amount of treatment Amount of
Press load Quantity of dissolved Concentration dissolved (i)
Surface shape of electricity Al of electrolyte Al Desmutting
R.sub.1 .DELTA.S a30 a60 brush roller (C/dm.sup.2) (g/m.sup.2)
(g/L) (g/m.sup.2) treatment (.mu.m)- (%) (%) (%) Example 2-1 7
Nitric acid/220 1.0 7.5 0.1 Performed 0.49 41 69.7 9.1 Example 2-2
7 Nitric acid/220 3.5 7.5 0.1 Performed 0.52 31 56.4 6.1
Comparative 7 Nitric acid/220 6.0 7.5 0.1 Performed 0.50 31 50.2
7.0 Example 2-1 Example 2-3 7 Nitric acid/220 1.0 7.5 1.0 Performed
0.52 39 60.3 5.0 Comparative 7 Nitric acid/220 1.0 7.5 5.0
Performed 0.50 28 57.0 3.3 Example 2-2 Example 2-4 7 Nitric
acid/220 1.0 2.5 0.1 Performed 0.51 40 67.2 5.7 Example 2-5 7
Nitric acid/220 1.0 5.0 0.1 Performed 0.53 35 64.8 6.0 Comparative
7 Nitric acid/220 1.0 10.0 0.1 Performed 0.49 29 68.0 7.1 Example
2-3 Example 2-6 -- Hydrochloric acid/ 6.0 -- -- -- 0.78 30 55.5 5.2
1500 Comparative -- Hydrochloric acid/ 1.0 -- -- -- 0.74 35 60.0
12.3 Example 2-4 1500 Comparative -- Hydrochloric acid/ 6.0 -- --
-- 0.60 22 46.2 2.4 Example 2-5 800 Comparative -- Hydrochloric
acid + 10 -- -- -- 0.53 28 55.9 4.3 Example 2-6 Acetic acid/800
Comparative -- Nitric acid/400 1.0 -- -- -- 0.69 41 59.5 12.1
Example 2-7 Comparative -- Nitric acid/400 5.0 -- -- -- 0.60 28
56.0 8.7 Example 2-8 Comparative 7 Nitric acid/220 3.5 -- -- --
0.59 29 52.2 6.0 Example 2-9 Comparative 3 Nitric acid/220 1.0 --
-- -- 0.40 45 62.5 15.0 Example 2-10 Comparative 3 Nitric acid/220
5.0 -- -- -- 0.39 39 57.0 9.4 Example 2-11
TABLE-US-00010 TABLE 3 Presensitized plate Printing characteristics
Support for Scum lithographic Image Scum resistance Inspectability
printing recording resis- Press after being of plate layer tance
life left plate Example 2-1 A 8 140 8 .largecircle. Example 2-2 A 9
120 8 .largecircle. Comparative A 10 80 8 .largecircle. Example 2-1
Example 2-3 A 8 120 8 .largecircle. Comparative A 9 80 6
.largecircle. Example 2-2 Example 2-4 A 10 120 7 .largecircle.
Example 2-5 A 10 100 7 .largecircle. Comparative A 7 60 6
.largecircle. Example 2-3 Example 2-6 A 7 100 7 .largecircle.
Comparative A 4 150 2 .largecircle. Example 2-4 Comparative A 7 60
7 .largecircle. Example 2-5 Comparative A 8 120 3 .DELTA. Example
2-6 Comparative A 4 100 4 .DELTA.X Example 2-7 Comparative A 5 80 5
.DELTA.X Example 2-8 Comparative A 6 100 6 .largecircle. Example
2-9 Comparative A 7 80 6 .DELTA. Example 2-10 Comparative A 7 60 6
.DELTA. Example 2-11
TABLE-US-00011 TABLE 4 Presensitized plate Support for Printing
characteristics lithographic Image Scum resistance printing
recording Scum Press after being left plate layer resistance life
Developer 2 Developer 1 Example 2-1 B 8 140 8 8 Example 2-2 B 9 120
8 8 Comparative B 10 80 8 8 Example 2-1 Comparative B 9 60 2 6
Example 2-2 Example 2-4 B 10 120 7 7 Comparative B 7 80 4 6 Example
2-3 Example 6 B 7 80 7 7 Comparative B 7 60 6 7 Example 2-5
Comparative B 4 100 2 4 Example 2-7 Comparative B 6 80 4 6 Example
2-9
<Example of the Third Aspect According to the Present
Invention> 3-1. Preparation of a Support for a Lithographic
Printing Plate
Example 3-1
The aforementioned surface treatments (a) to (i) were performed on
an aluminum plate in the same method as in Example 1-9, except that
the amount of the aluminum plate dissolved was set at 3.5 g/m.sup.2
in (e) mentioned above.
Continuously, a water receptive layer was formed and a
presensitized plate according to the present invention was prepared
by providing an image recording layer. However, before that, a
factor that specifies the physical properties on the surface of an
aluminum plate was measured. In addition, the support prepared in
Example 3-1 (before the formation of a water receptive layer) was
determined to be "Support A".
Examples 3-2 to 3-4 and Comparative Examples 3-1 to 3-5
Supports according to Examples 3-2 to 3-4 and Comparative Examples
3-1 to 3-5 on which water receptive layers were not yet formed were
obtained (determined to be "Support B" to "Support I" in order) in
the same method as in Example 3-1, except that the conditions of
each treatment were changed as shown in Table 5. In addition, "-"
in Table 5 indicates that no treatment was performed.
3-2. Calculation of a Factor on the Surface Shape of a Support for
a Lithographic Printing Plate
With regard to the surface of a support for a lithographic printing
plate obtained above, R.sub.a, .DELTA.S, a30 and a60 were taken in
the same methods as in the examples of the second aspect according
to the present invention as mentioned above.
The results were shown in Table 5.
3-3. Preparation of a Presensitized Plate
Examples 3-5 to 3-20 and Comparative Examples 3-6 to 3-43
A water receptive layer was formed on the supports A to I prepared
in Examples 3-1 to 3-4 and Comparative Examples 3-1 to 3-5 in the
combinations as shown in Table 6 in the following methods.
<Water Receptive Layer Formation Process I>
By using the anodizing device having a structure shown in FIG. 4,
Anodizing treatment was carried out to obtain a support for a
lithographic printing plate. An electrolyte supplied for each of
the first and second electrolytic portions was sulfuric acid. For
each electrolyte, the concentration of sulfuric acid was 170 g/L
(containing 0.5 wt % of aluminum ion) and a temperature was
38.degree. C. Then, washing was performed by spraying water. The
final amount of an anodized layer was 2.7 g/m.sup.2.
The thermal conductivity of an anodized layer was measured with the
aforementioned device and the average value of measurements at 5
points was found. When measuring the thermal conductivity, metal
aluminum and aluminum oxide (alumina) were measured every time and
a compensation was made by comparing the measured values with each
referential value. As the thermal conductivity was found by the
following formula [1], it was 0.4 W/(mK).
.times..times..times..times..times..times..times..times..times..times.
##EQU00004## <Water Receptive Layer Formation Process II>
First, water receptive layer formation process I was performed.
Pore widening treatment (PW treatment) was then performed to lower
the thermal conductivity of an anodized layer. Pore widening
treatment was performed by dipping a plate in a sodium hydroxide
aqueous solution controlled at pH 13 at 30.degree. C. for 70
sec.
The final amount of an anodized layer was 1.6 g/m.sup.2. As the
thermal conductivity of an anodized layer was found as in the
aforementioned, it was 0.05 W/(mK).
(Water Receptive Layer Formation Process III>
The treatment was performed in the same conditions as in water
receptive layer formation process I, except that oxalic acid was
used as an electrolyte.
As the thermal conductivity of an anodized layer was found, it was
0.2 W/(mK).
<Water Receptive Layer Formation Process IV>
A SiO.sub.2 layer was vapor deposited on a support with a generally
used reactive sputtering process. Concretely, the treatment was
performed using SiO.sub.2 as a target with a high-frequency power
supply of 500 W at a pressure of 6.7.times.10.sup.-1 Pa for 20
minutes and 30 seconds to provide a SiO.sub.2 layer of 0.2 .mu.m.
As the thermal conductivity of a SiO.sub.2 layer was found, it was
0.2 W/(mK).
<Water Receptive Layer Formation Process V>
An aluminum layer was vapor deposited on a support with a generally
used magnetron sputtering process. Concretely, an aluminum layer
having a thickness of 0.2 .mu.m was provided with an ordinary vapor
deposition method.
As the thermal conductivity of an aluminum layer was found, it was
237 W/(mK).
<Water Receptive Layer Formation Process VI>
An Al.sub.2O.sub.3 layer was vapor deposited on a support with a
generally used reactive sputtering process. Concretely, the
treatment was performed using Al.sub.2O.sub.3 as a target with a
high-frequency power supply of 500 W at a pressure of
6.7.times.10.sup.-1 Pa for 44 minutes and 45 seconds to provide an
Al.sub.2O.sub.3 layer having a thickness of 0.2 .mu.m. As the
thermal conductivity of an Al.sub.2O.sub.3 layer was found, it was
36 W/(mK).
A presensitized plate was obtained by providing a thermal positive
working image recording layer in the same method as in the example
of the first aspect according to the present invention on each
support for a lithographic printing plate obtained in the
aforementioned after a water receptive layer was formed.
4. Exposure and Development Treatment
A lithographic printing plate was obtained by performing image
exposure and development treatment on each presensitized plate
obtained in the aforementioned in the following method.
Exposure was performed as to allow an amount of printing plate
energy to be changed to 10, 20, 30, 40, 50, 60, 70, 80, 90, 100,
120, 150, 170, 200, 400 and 800 mJ/cm.sup.2 with main scanning
speed fixed at 1 m/sec. using CREO Inc.-made TrenndSetter3244
equipped with a semiconductor laser of wavelength 830 nm and beam
diameter 8 .mu.m (1/e.sup.2). Note that, a plate with exposure so
performed as to allow an amount of printing plate energy to be 150
mJ/cm.sup.2 was used to evaluate scum resistance and press life to
be described later.
Development treatment was then performed with developer 2. This
development was performed with an automatic processor PS900NP (made
by Fuji Photo Film Co., Ltd.) filled with the aforementioned alkali
developer under the conditions at a development temperature of
25.degree. C. for 12 seconds. After the development treatment was
finished, treatment with gum (GU-7 (1:1)) or the like were
performed, and a lithographic printing plate was obtained with
plate making completed.
5. Evaluation of a Presensitized Plate and a Lithographic Printing
Plate
Scum resistance and press life of the lithographic printing plate
obtained as mentioned above and the sensitivity of a presensitized
plate were evaluated in the following method.
(1) Scum Resistance
With regard to a lithographic printing plate using supports A to I
after a SiO.sub.2 layer was provided thereon, scum resistance was
evaluated in the same method as in the example of the first aspect
according to the present invention as mentioned above.
The results were shown in Table 5.
(2) Press Life
With regard to a lithographic printing plate using supports A to I
after the SiO.sub.2 layer was provided on them, press life was
evaluated in the same method as in the example of the first aspect
according to the present invention as mentioned above.
The results were shown in Table 5. In addition, press life is
expressed in a relative value that the number of printed sheets
performed by a lithographic printing plate where a support for a
lithographic printing plate in Example 3-4 is provided with the
image recording layer was determined to be 100.
(3) Sensitivity
Sensitivity was evaluated by an exposure amount when a degree of
whiteness in non-image areas after development treatment was
performed became the same as in that of a support.
The results were shown in Table 6. Note that, it indicated that the
smaller the amount of an exposure (amount of printing plate
energy), the higher the sensitivity as development could be
performed by a lower exposure, and on the contrary, the larger the
amount of an exposure is, the lower the sensitivity as development
could not be performed unless an exposure is high.
TABLE-US-00012 TABLE 5 Conditions of surface treatment Process (d)
Process (e) Process (h) Printing Process (a) Electrolyte/ Amount of
Process (g) Amount of characteristics Press load Quantity of
dissolved Concentration dissolved Scum Sup- of brush electricity Al
of electrolyte Al Pro- Surface Shape resis- Press port roller
(C/dm.sup.2) (g/m.sup.2) (g/L) (g/m.sup.2) cess (i) R.sub.a
.DELTA.S a30 a60 tance life Example 3-1 A 7 Nitric acid/220 3.5 7.5
0.1 Per- 0.52 31 56.4 6.1 10 120 formed Example 3-2 B 7 Nitric
acid/220 6.0 2.5 0.1 Per- 0.51 40 67.2 5.7 9 120 formed Example 3-3
C 7 Nitric acid/220 6.0 5.0 0.1 Per- 0.53 35 64.8 6.0 9 100 formed
Example 3-4 D -- Hydrochloric 6.0 -- -- -- 0.78 30 55.5 5.2 7 100
acid/1500 Comparative E 7 Nitric acid/220 6.0 7.5 0.1 Per- 0.50 31
50.2 7.0 9 80 Example 3-1 formed Comparative F 7 Nitric acid/220
6.0 10.0 0.1 Per- 0.49 29 68.0 7.1 7 60 Example 3-2 formed
Comparative G -- Hydrochloric 6.0 -- -- -- 0.60 22 46.2 2.4 7 60
Example 3-3 acid/800 Comparative H -- Nitric acid/400 1.0 -- -- --
0.69 41 59.5 12.1 5 100 Example 3-4 Comparative I 7 Nitric acid/220
3.5 -- -- -- 0.59 29 52.2 6.0 6 100 Example 3-5
TABLE-US-00013 TABLE 6 Water receptive layer Sensitivity Support
formation process (mJ/cm.sup.2) Example 3-5 A I 70 Example 3-6 A II
40 Example 3-7 A III 50 Example 3-8 A IV 50 Example 3-9 B I 70
Example 3-10 B II 40 Example 3-11 B III 50 Example 3-12 B IV 50
Example 3-13 C I 70 Example 3-14 C II 40 Example 3-15 C III 50
Example 3-16 C IV 50 Example 3-17 D I 70 Example 3-18 D II 40
Example 3-19 D III 50 Example 3-20 D IV 50 Comparative Example 3-6
A V 800 Comparative Example 3-7 A VI 150 Comparative Example 3-8 B
V 800 Comparative Example 3-9 B VI 150 Comparative Example 3-10 C V
800 Comparative Example 3-11 C VI 150 Comparative Example 3-12 D V
800 Comparative Example 3-13 D VI 150 Comparative Example 3-14 E I
70 Comparative Example 3-15 E II 40 Comparative Example 3-16 E III
50 Comparative Example 3-17 E IV 50 Comparative Example 3-18 E V
800 Comparative Example 3-19 E VI 150 Comparative Example 3-20 F I
80 Comparative Example 3-21 F II 50 Comparative Example 3-22 F III
60 Comparative Example 3-23 F IV 60 Comparative Example 3-24 F V
800 Comparative Example 3-25 F VI 170 Comparative Example 3-26 G I
65 Comparative Example 3-27 G II 40 Comparative Example 3-28 G III
50 Comparative Example 3-29 G IV 50 Comparative Example 3-30 G V
800 Comparative Example 3-31 G VI 150 Comparative Example 3-32 H I
80 Comparative Example 3-33 H II 50 Comparative Example 3-34 H III
60 Comparative Example 3-35 H IV 60 Comparative Example 3-36 H V
900 Comparative Example 3-37 H VI 200 Comparative Example 3-38 I I
75 Comparative Example 3-39 I II 45 Comparative Example 3-40 I III
50 Comparative Example 3-41 I IV 50 Comparative Example 3-42 I V
800 Comparative Example 3-43 I VI 170
As apparent from Tables 5 and 6, a presensitized plate according to
the present invention using the support for a lithographic printing
plate of the third aspect according to the present invention,
wherein R.sub.a, .DELTA.S, a30 and a60 obtained from the
three-dimensional data taken by measuring 512.times.512 points in
50 .mu.m-square on the surface of a plate with an atomic force
microscope each meets the specified conditions (Examples 3-1 to
3-4) and a water receptive layer that the thermal conductivity
meets the specified conditions was formed on its surface, was
excellent in both scum resistance and press life when a
lithographic printing plate was prepared. It also had a sufficient
performance even if an exposure was lower since the sensitivity was
higher.
* * * * *